ALBERT

Description: The first-principle theoretical studies about the effects of the electric field and oxygen vacancies on the structural relaxation of rutile titanium dioxide and the impacts of the relaxed structures on the capacitor-voltage curves are reported. The results show that oxygen vacancies in the same side bring more unstable bonds between oxygen atoms and titanium atoms than they do in the two sides. Titanium atoms dominate the interactions with oxygen vacancies on the unstable bonds. The unstable bonds of Ti-O would be broken at an electric field of 2.6 MV/cm. The broken bonds caused by the electric field and oxygen vacancies can form the conduction path in rutile titanium dioxide. The static dielectric constants are dependent on the dispersion of oxygen vacancies. It is concluded that the capacitor-voltage curves of Metal/TiO 2 /P-Si structure are dependent on the oxygen vacancies. It can help us to clarify the atom-level mechanism of the conduction path in resistive switching in resistance random-access memory.

Description: The way in which information about behavior is represented at different levels of the motor pathway, remains among the fundamental unresolved problems of motor coding and sensorimotor integration. Insight into this matter is essential for understanding complex learned behaviors such as speech or birdsong. A major challenge in motor coding has been to identify an appropriate framework for characterizing behavior. In this work we discuss a novel approach linking biomechanics and neurophysiology to explore motor control of songbirds. We present a model of song production based on gestures that can be related to physiological parameters that the birds can control. This physical model for the vocal structures allows a reduction in the dimensionality of the behavior, being a powerful approach for studying sensorimotor integration. Our results also show how dynamical systems models can provide insight into neurophysiological analysis of vocal motor control. In particular, our work challenges the actual understanding of how the motor pathway of the songbird systems works and proposes a novel perspective to study neural coding for song production.

Description: With the recent advances of experimental techniques, the nonlinear ultrafast optical response of metal nano-objects can now be investigated both on ensembles and on single nanoparticles. Its connection with the metal electronic and lattice kinetics is studied on the basis of a model describing the wavelength and time-dependent modifications of the object material dielectric function. Its application is illustrated in the case of single silver nanospheres and gold nanorods, as well as on ensembles of noble metal nanoparticles and metal-semiconductor nano-hybrids. This quantitative analysis also permits to elucidate the physical mechanisms at the origin of ultrafast nonlinearities in confined metals at different timescales.

Description: The yearly aggregated tax income data of all, more than 8000, Italian municipalities are analyzed for a period of five years, from 2007 to 2011, to search for conformity or not with Benford’s law, a counter-intuitive phenomenon observed in large tabulated data where the occurrence of numbers having smaller initial digits is more favored than those with larger digits. This is done in anticipation that large deviations from Benford’s law will be found in view of tax evasion supposedly being widespread across Italy. Contrary to expectations, we show that the overall tax income data for all these years is in excellent agreement with Benford’s law. Furthermore, we also analyze the data of Calabria, Campania and Sicily, the three Italian regions known for strong presence of mafia, to see if there are any marked deviations from Benford’s law. Again, we find that all yearly data sets for Calabria and Sicily agree with Benford’s law whereas only the 2007 and 2008 yearly data show departures from the law for Campania. These results are again surprising in view of underground and illegal nature of economic activities of mafia which significantly contribute to tax evasion. Some hypothesis for the found conformity is presented.

Description: Core-level photoemission spectra of the Fabre salts with X = SbF 6 and PF 6 were taken using hard X-rays from PETRA III, Hamburg. In these salts TMTTF layers show a significant stack dimerization with a charge transfer of 1 e per dimer to the anion SbF 6 or PF 6 . At room temperature and slightly below the core-level spectra exhibit single lines, characteristic for a well-screened metallic state. At reduced temperatures progressive charge localization sets in, followed by a 2nd order phase transition into a charge-ordered ground state. In both salts groups of new core-level signals occur, shifted towards lower kinetic energies. This is indicative of a reduced transverse-conductivity across the anion layers, visible as layer-dependent charge depletion for both samples. The surface potential was traced via shifts of core-level signals of an adsorbate. A well-defined potential could be established by a conducting cap layer of 5 nm aluminum which appears “transparent” due to the large probing depth of HAXPES (8–10 nm). At the transition into the charge-ordered phase the fluorine 1 s line of (TMTTF) 2 SbF 6 shifts by 2.8 eV to higher binding energy. This is a spectroscopic fingerprint of the loss of inversion symmetry accompanied by a cooperative shift of the SbF 6 anions towards the more positively charged TMTTF donors. This shift does not occur for the X = PF 6 compound, most likely due to smaller charge disproportion or due to the presence of charge disorder.

Description: We studied the structural and dynamical properties of amorphous germanium dioxide (GeO 2 ) from low to high pressure by means of the classical molecular dynamics technique. The simulations were done in the micro-canonical ensemble, with systems at densities ranged from 3.16 to 6.79 g/cm 3 , using a pairwise potential. The network topology of the systems is analyzed at atomic level through partial pair correlations, coordination number and angular distributions. The dynamic properties were characterized by means of the vibrational density of states. According the density increases, a structural transformation from a short-range order, defined by a building block composed by a basic (GeO 4 ) tetrahedron, to a basic (GeO 6 ) octahedron is observed. The vibrational density of states also presents important changes when the density increases, with a low frequency band lessened, and a high density band wider and flatter.

Description: We apply the renormalized perturbation theory (RPT) to the symmetric Anderson impurity model. Within the RPT framework exact results for physical observables such as the spin and charge susceptibility can be obtained in terms of the renormalized values \(\tilde \mu = (\tilde \Delta ,\tilde U)\) of the hybridization Δ and Coulomb interaction U of the model. The main difficulty in the RPT approach usually lies in the calculation of the renormalized values themselves. In the present work we show how this can be accomplished by deriving differential flow equations describing the evolution of \(\tilde \mu = (\tilde \Delta )\) with Δ . By exploiting the fact that \(\tilde \mu = (\tilde \Delta )\) can be determined analytically in the limit Δ → ∞ we solve the flow equations numerically to obtain estimates for the renormalized parameters in the range 0 〈 U / πΔ 〈 3.5.

Description: A simple method has been introduced to render the equilibrium solution of the Wigner equation for all orders of the quantum correction. This process generates a recursion relation involving the coefficients of the different powers of the momentum. The technique relies on an appropriate guess for the trial solution and differs from the Wigner’s original work. The solution is yielded in a compact exponential form with a polynomial of momentum in the argument and regains Wigner’s form when expansion of the exponential factor is carried out. The study is also important in the investigation of various closed as well as open quantum mechanical systems. In addition, this solution may be employed to obtain the nonequilibrium one particle Wigner distribution in the relaxation-time approximation and under near-equilibrium condition.

Description: We study charge transport in a graphene zigzag nanoribbon driven by an external time-periodic kicking potential. Using the exact solution of the time-dependent Dirac equation with a delta-kick potential acting in each period, we study the time evolution of the population transfer probability and the time-dependent optical conductivity. By variation of the kicking parameters, the conductivity becomes widely tunable.

Description: We investigate the network formed by the collaboration of researchers seeking funding by the European Commission by submitting research proposals. Institutions are network nodes and collaborations are links between the nodes. We constructed one network for the accepted proposals and one for the rejected ones, in order to look for any structural differences between them. To this end, first, we compare the size of the largest connected components and the resulting degree distributions. The latter show notable difference only in the region of relatively small degrees. We calculate the assortative mixing by participant type, i.e. a property which indicates whether the participant is a university/research institute, a company (non-profit included), or undefined. By aggregating the data of both networks into three geographical scales (city, region, country), we compare the degree assortativity and average node weight, in all scales. With respect to these two features the networks display similar behaviour. Finally, we compare a series of centrality measures and the Minimum Spanning Trees, at the country scale, to assess the relative performance of the countries. We find that five countries, France, Germany, the United Kingdom, Spain and Italy, play a central role in both networks, however, their relative significance is not the same.

Description:    We report molecular dynamics calculations on the evolution of Co-Au and Ag-Au alloy nanowires stretched along the [100], [110] and [111] crystallographic directions. The strong tendency of chain formation has been found for Ag-Au alloy. On the contrary the Co-Au alloy presents a different breaking pattern. In particular, we have found the formation of tetramer alloy nanowires. Finally, we present the mechanical properties of alloy nanocontacts. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-30352-3 Authors A. L. Klavsyuk, Faculty of Physics, Moscow State University, 119991 Moscow, Russian Federation S. V. Kolesnikov, Faculty of Physics, Moscow State University, 119991 Moscow, Russian Federation I. K. Gainullin, Faculty of Physics, Moscow State University, 119991 Moscow, Russian Federation A. M. Saletsky, Faculty of Physics, Moscow State University, 119991 Moscow, Russian Federation Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    Using X-microtomography and non equilibrium classical molecular dynamics, we present a study of the elementary processes of spallation of single crystal tantalum. The single crystal is illuminated by a laser pulse which induces the propagation of a strong unsustained shock. The analysed data mainly are number and shape of pores resulting from the tensile inside the material when the incident shock reflects on the opposite face. Experimental pores size distribution exhibits two power laws attributed to the growth and the coalescence stages. The average pore shape is ellipsoid with main axis along the shock axis propagation. This first part is completed by a large scale molecular dynamics simulation mimics at reduced scale the real experiment. After preliminary calculations validating the chosen potential function the formation and shock propagation is detailed. Then we extract from the simulation similar data than in experiment. The pores size distribution shows three power laws identified as the nucleation, the growth and the coalescence stages. The slopes of the two last stages are very similar to the experimental one, confirming the scale invariance of this data as suggested by their analytical form. The general pore shape also is close to the experiment shape but with a different orientation (perpendicular to the shock propagation axis). Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1140/epjb/e2012-30269-9 Authors L. Soulard, CEA, DAM, DIF, 91297 Arpajon, France J. Bontaz-Carion, CEA, DAM, DIF, 91297 Arpajon, France J. P. Cuq-Lelandais, CEA, DAM, Valduc, 21120 Is-sur-Tille, France Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    The modulational instability of a plane wave for the perturbed non-integrable Ablowitz-Ladik equation for α -helix proteins is analyzed. Through the linear stability analysis, we observe that the presence of additional terms in the Ablowitz-Ladik equation tends to suppress modulational instability. Numerical simulations are performed in order to verify our analytical predictions. The presence of extended terms in the Ablowitz-Ladik equation tends to compactify and split the emerging localized structures. Particular attention is paid to the emergence of multi-hump structures, and the biological relevance of the latter is discussed. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-21076-5 Authors R. Y. Ondoua, Laboratory of Biophysics, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon C. B. Tabi, Laboratory of Biophysics, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon H. P. Ekobena Fouda, Laboratory of Biophysics, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon A. Mohamadou, Laboratory of Biophysics, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon T. C. Kofané, Laboratory of Mechanics, Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 9

Description:    In a recent publication [J.A. Berger, L. Reining, F. Sottile, Phys. Rev. B 82 , 041103(R) (2010)] we introduced the effective-energy technique to calculate in an accurate and numerically efficient manner the GW self-energy as well as the polarizability, which is required to evaluate the screened Coulomb interaction W . In this work we show that the effective-energy technique can be used to further simplify the expression for the polarizability without a significant loss of accuracy. In contrast to standard sum-over-state methods where huge summations over empty states are required, our approach only requires summations over occupied states. The three simplest approximations we obtain for the polarizability are explicit functionals of an independent- or quasi-particle one-body reduced density matrix. We provide evidence of the numerical accuracy of this simplified effective-energy technique as well as an analysis of our method. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-30237-5 Authors J. A. Berger, Laboratoire de Chimie et Physique Quantiques, (UMR 5626 du CNRS), IRSAMC, Université P. Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France L. Reining, Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM, 91128 Palaiseau, France F. Sottile, Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM, 91128 Palaiseau, France Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 9

Description:    Heat conduction is an important energy transport process in nature. Phonon is the major energy carrier for heat in semiconductors and dielectric materials. In analogy to Ohm’s law of electrical conduction, Fourier’s law is the fundamental law of heat conduction in solids. Although Fourier’s law has received great success in describing macroscopic heat conduction in the past two hundred years, its validity in low dimensional systems is still an open question. Here we give a brief review of the recent developments in experimental, theoretical and numerical studies of heat conduction in low dimensional systems, including lattice models and low dimensional nanostructures such as nanowires, nanotubes and graphene. We will demonstrate that phonons transport in low dimensional systems superdiffusively, which leads to a size dependent thermal conductivity. In other words, Fourier’s law is not applicable in low dimensional structures. Content Type Journal Article Category Colloquium Pages 1-20 DOI 10.1140/epjb/e2012-30383-8 Authors S. Liu, NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 117456 Singapore, Republic of Singapore X. F. Xu, Centre for Computational Science and Engineering, Graphene Research Centre, Department of Physics, National University of Singapore, 117546 Singapore, Republic of Singapore R. G. Xie, Centre for Computational Science and Engineering, Graphene Research Centre, Department of Physics, National University of Singapore, 117546 Singapore, Republic of Singapore G. Zhang, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing, 100871 P.R. China B. W. Li, NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 117456 Singapore, Republic of Singapore Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    In this paper, we present a study of magnetic properties of NiFe thin film deposited onto polymer substrate (Kapton®). A complete study of the magnetic anisotropy is made thanks to ferromagnetic resonance. In-plane and out-of-plane anisotropies in the film are obtained due to the elaboration process. Furthermore, the magnetization is manipulated by applying uniaxial stress in the film. The stress-induced apparition of stripes domains from a saturated configuration is evidenced by in situ Brillouin light scattering and magnetic force microscopy studies. The saturating field is derived from the Muller criterion. The magnetostriction coefficient is evaluated from the applied stress allowing the stripes domains regeneration. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-30274-0 Authors W. Karboul-Trojet, LSPM-CNRS (UPR 3407), Université Paris 13, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse, France Y. Roussigné, LSPM-CNRS (UPR 3407), Université Paris 13, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse, France D. Faurie, LSPM-CNRS (UPR 3407), Université Paris 13, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse, France S. M. Chérif, LSPM-CNRS (UPR 3407), Université Paris 13, 99 avenue Jean-Baptiste Clément, 93430 Villetaneuse, France Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    The influence of an external electric field on the binding energies of the ground state and excited states with the third-harmonic-generation (THG) coefficient for spherical quantum dot (QD) with parabolic confinement is investigated theoretically. The energy levels and wave functions of electronic states in the QDs are calculated using by variational method within the effective-mass approximation. The numerical results demonstrate that the THG coefficient very sensitively depends on the magnitude of the electric field and the radius of the QDs. In addition, the THG coefficient also depends on the relaxation rate of the spherical QD with parabolic confinement and the position of impurity. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-30361-2 Authors M. Kirak, Department of Science Education, Faculty of Education, Bozok University, 66100 Yozgat, Turkey Y. Altinok, Institute of Science, Bozok University, 66100 Yozgat, Turkey Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    We have investigated the complex magnetic properties of Fe 1− x Mn x C y alloys by using an iterative combination of ab initio calculations and Monte Carlo simulations. The latter gives insight into finite temperature magnetism and allows to determine the critical temperature of magnetic phase transitions. We restrict the investigation to ordered systems with 25, 50 and 75% manganese and study the influence of carbon at octahedral interstitial sites on the magnetic properties. The combination of ab initio calculations with Monte Carlo simulations turns out to be a powerful tool to determine the complex magnetic structures, which originate from the competition of ferro- and antiferromagnetic interactions in the FeMn alloys. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1140/epjb/e2012-30321-x Authors D. Comtesse, Faculty of Physics, University of Duisburg-Essen and CENIDE, 47048 Duisburg, Germany H. C. Herper, Faculty of Physics, University of Duisburg-Essen and CENIDE, 47048 Duisburg, Germany A. Hucht, Faculty of Physics, University of Duisburg-Essen and CENIDE, 47048 Duisburg, Germany P. Entel, Faculty of Physics, University of Duisburg-Essen and CENIDE, 47048 Duisburg, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    We show how exact diagonalization of small clusters can be used as a fast and reliable impurity solver by determining the phase diagram and physical properties of the bosonic single-impurity Anderson model. This is specially important for applications which require the solution of a large number of different single-impurity problems, such as the bosonic dynamical mean field theory of disordered systems. In particular, we investigate the connection between spontaneous global gauge symmetry breaking and the occurrence of Bose-Einstein condensation (BEC). We show how BEC is accurately signaled by the appearance of broken symmetry, even when a fairly modest number of states is retained. The occurrence of symmetry breaking can be detected both by adding a small conjugate field or, as in generic quantum critical points, by the divergence of the associated phase susceptibility. Our results show excellent agreement with the considerably more demanding numerical renormalization group (NRG) method. We also investigate the mean impurity occupancy and its fluctuations, identifying an asymmetry in their critical behavior across the quantum phase transitions between BEC and ‘Mott’ phases. Content Type Journal Article Category Regular Article Pages 1-9 DOI 10.1140/epjb/e2012-30191-2 Authors J. H. Warnes, Instituto de Física Gleb Wataghin, Rua Sérgio Buarque de Holanda, 777, CEP 13083-859 Campinas, SP, Brazil E. Miranda, Instituto de Física Gleb Wataghin, Rua Sérgio Buarque de Holanda, 777, CEP 13083-859 Campinas, SP, Brazil Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    Employing the extended dynamical mean field theory (EDMFT) and the quantum Monte Carlo (QMC) method, we investigate the effect of the spatial fluctuations in the two-band Hubbard model with anisotropic bandwidth in the vicinity of the Mott metal-insulator transition. At half filling, we demonstrate that while the inclusion of the non-local spin-spin interaction amounts to enhancing the correlation and suppressing the metallic character, the orbitally selective Mott transition (OSMT) remains stable for various strengths of the non-local correlation. The same is true when the system is doped away from half filling. The OSMT phase is evidenced at low dopant concentration and the simultaneous metallic phase emerges at overdoped regime. From the analysis of the self energy, it follows that the nature of the metallic phase upon doping violates the Fermi liquid character and persists at considerably large doping. Our theory also offers a new perspective for the investigation of the non-local fluctuation in the multi-orbital system within the single-site scheme. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-30198-7 Authors B. D. Napitu, Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany J. Berakdar, Institut für Physik, Martin-Luther-Universität, Halle-Wittenberg, 06099 Halle, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    The dynamic behavior of a two-sublattice spin-2 Ising model with a crystal-field interaction in the presence of a time-dependent oscillating external magnetic field on a hexagonal lattice is studied by using the Glauber-type stochastic dynamics. The lattice is formed by alternate layers of spins σ  = 2 and S  = 2. We employ the Glauber transition rates to construct the mean-field dynamic equations. First, we study the time variations of the average sublattice magnetizations to find the phases in the system, and the thermal behavior of the dynamic sublattice magnetizations to characterize the nature (continuous and discontinuous) of the phase transitions and to obtain the dynamic phase transition (DPT) points. Then, the behavior of the dynamic total magnetization as a function of the temperature is investigated to find the dynamic compensation temperatures as well as to determine the type of compensation behavior. We present the dynamic phase diagrams including the dynamic compensation temperatures in the nine different planes. Phase diagrams contain the paramagnetic ( p ), antiferromagnetic-1 ( a f 1 ), antiferromagnetic-2 ( a f 2 ) and ferrimagnetic ( i ) fundamental phases, five different mixed phases and the compensation temperature or the L -type behavior that strongly depend on the interaction parameters. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-30607-y Authors Ü. Temizer, Department of Physics, Bozok University, 66200 Yozgat, Turkey T. Korkmaz, Institute of Science, Bozok University, 66200 Yozgat, Turkey Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    We investigate the electronic and magnetic properties of NiS 2 , which, by varying the chemical composition substituting S by Se atoms or applying pressure, can be driven across various electronic and magnetic phase transitions. By combining several theoretical methods, we highlight the different role played by the chalcogen dimers and the volume compression in determining the phase transitions, through variations of the chalcogen p bonding-antibonding gap, the crystal-field splitting and the broadening of the bandwidths. While the generalized gradient approximation (GGA) of density-functional theory fails to reproduce the insulating nature of NiS 2 , it describes well the magnetic boundaries of the phase diagram. The large GGA delocalization error is corrected to a large extent by the use of GGA + U, hybrid functionals or the self-consistent COHSEX + GW approximation. We also discuss the advantages and the shortcomings of the different approximations in the various regions of the phase diagram of this prototypical correlated compound. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-30384-7 Authors Cosima Schuster, Institut für Physik, Universität Augsburg, D-86135 Augsburg, Germany Matteo Gatti, Nano-Bio Spectroscopy Group and ETSF Scientific Development Center, Dpto. Física de Materiales, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Universidad del País Vasco UPV/EHU, Avenida Tolosa 72, E-20018 San Sebastián, Spain Angel Rubio, Nano-Bio Spectroscopy Group and ETSF Scientific Development Center, Dpto. Física de Materiales, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Universidad del País Vasco UPV/EHU, Avenida Tolosa 72, E-20018 San Sebastián, Spain Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 9

Description:    Statistical physics has been applied in the last decades to several problems in mechanics, including fracture and plasticity. Concept drawn from percolation, fractal geometry, phase-transitions, and interface depinning have been used with varying degrees of success to understand these problems. In this colloquium, I describe recent successes and current challenging problems for statistical physics in fracture and plasticity, focusing on the roughness of cracks, fracture size effects and micron-scale plasticity. Content Type Journal Article Category Colloquium Pages 1-12 DOI 10.1140/epjb/e2012-30471-9 Authors S. Zapperi, CNR - Consiglio Nazionale delle Ricerche, IENI, Via R. Cozzi 53, 20125 Milano, Italy Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 9

Description:    We report key advances in the area of GW calculations, review the available software implementations and define standardization criteria to render the comparison between GW calculations from different codes meaningful, and identify future major challenges in the area of quasiparticle calculations. This Topical Issue should be a reference point for further developments in the field. Content Type Journal Article Category Editorial Pages 1-2 DOI 10.1140/epjb/e2012-30691-y Authors F. Giustino, Department of Materials, University of Oxford, OX1 3PH Oxford, UK P. Umari, Dipartimento di Fisica e Astronomia, Università degli studi di Padova, via Marzolo 8, 35131 Padova, Italy A. Rubio, Nano-Bio Spectroscopy Group and ETSF Scientific Development Center, Universidad del País Vasco, CFM CSIC-UPV/EHU-MPC and DIPC, Avenida Tolosa 72, 20018 Donostia, Spain Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 9

Description:    Density functional theory (DFT) combined with the non equilibrium Green’s function formalism (NEGF) is applied to perform spin polarized transport calculations on small world network (SWN) systems consisting of atomic wires. Including the spin property in SWN structures leads to interesting electrical properties. It is revealed that the emerging spin polarization depends mainly on the SWN geometry given by the asymmetric distribution of loops joining the arbitrary atoms on the main chain. The spin-asymmetric behavior which yields the spin polarization is found to be largely determined by those loops which are close to the electrodes. However, spin polarization may vanish for a specific SWN structure due to symmetry. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-30253-5 Authors S. Caliskan, Physics Department, Fatih University, Buyukcekmece, 34500 Istanbul, Turkey M. Canturk, Department of Computer Engineering, Turgut Özal University, Ayvali Mah. Gazze. Cad. No: 7 Etlik- Keçiören, 06010 Ankara, Turkey Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 9

Description:    The electronic properties of three different oxides (ZnO, SnO 2 and SiO 2 ) are investigated within many-body perturbation theory in the G 0 W 0 approximation. The frequency dependence of the dielectric function is either approximated using two different well-established plasmon-pole models (one of which enforces the fulfillment of the f -sum rule) or treated explicitly by means of the contour-deformation approach. Comparing these results, it is found that the plasmon-pole model enforcing the f -sum rule gives less accurate results for all three oxides. The calculated electronic properties are also compared with the available experimental data and previous ab initio results, focusing on the d state binding energies. The G 0 W 0 approach leads to significantly improved band gaps with respect to calculations based on the density functional theory in the local density approximation. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-30121-4 Authors A. Miglio, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium D. Waroquiers, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium G. Antonius, Département de physique, Université de Montréal, C.P. 6128, Succursale Centre-Ville, H3C 3J7 Montréal, Canada M. Giantomassi, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium M. Stankovski, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium M. Côté, Département de physique, Université de Montréal, C.P. 6128, Succursale Centre-Ville, H3C 3J7 Montréal, Canada X. Gonze, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium G. -M. Rignanese, Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 9

Description:    Eigenstate bases are used to study electrical conductivity in graphene in the presence of short-range diagonal disorder and inter-valley scattering. For the first time, the behavior of graphene in a moderate and weak disorderd regime is presented. For disorder strength, W   /   t  ≥  5, the density of states is flat. A connection is then established with the work of Abrahams et al. using Microscopic Renormalization Group (MRG) approach. For disorder strength, W   /   t  = 5, results are in good agreement. For low disorder strength, W   /   t  = 2, energy-resolved current matrix elements squared for different locations of the Fermi energy from the band centre is studied. Explicit dependence of the current matrix elements on Fermi energy is shown. It is found that states close to the band centre are more extended and fall off nearly as 1/E l 2 as one moves away from the band centre. Further studies on current matrix elements versus disorder strength suggests a cross-over from weakly localized to a very weakly localized system. Using the Kubo-Greenwood formula, conductivity and mobility is calculated. For low disorder strength, conductivity is in a good qualitative agreement with the experiments, even for the on-site disorder. The intensity plots of the eigenstates also reveal clear signatures of puddle formation for very small carrier concentration. We also make comparision with square lattice and find that graphene is more easily localized when subject to disorder. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-20885-8 Authors R. Ray, Department of Physics, Indian Institute of Technology Kanpur, 208016 Kanpur, India Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    Jaynesian statistical inference is used to predict that steady, non-uniform Couette flow in a simple liquid will generate a heat flux proportional to the gradient of the square of the strain-rate when the temperature gradient is negligible. The heat flux is divided into phonon and self-diffusion components, with the latter coupling to the elastic strain and inelastic strain-rate. Operators for all these are substituted into the information-theoretic phase-space distribution. By taking moments of an exact equation for this distribution derived by Robertson, one obtains an evolution equation for the self-diffusion component of the heat flux which, in a steady state, predicts shear-driven heat flow. Content Type Journal Article Pages 287-292 DOI 10.1007/BF03219170 Authors R. E. Nettleton, Department of Physics, University of the Witwatersrand, Johannesburg, 2050 South Africa Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 2

Description:    Many experiments done on neutral lipid bilayers in pure water show weak repulsions. These weak forces prevent vesicles from adhering and are generally overcome by adding some salt in the aqueous medium. They also appear as stray repulsions in surface forces measurements made on lipid bilayers. Using a surface forces apparatus in pure water and in salt solution, we have measured the forces between two stearoyl-oleoyl-phosphatidyl-choline (SOPC) bilayers and between two dimiristoyl-phosphatidyl-ethanolamine (DMPE) bilayers. The results show that the repulsions are due to a small amount of negative charges coming from impurities in SOPC. This was quantitatively confirmed by electrophoretic measurements. There are 3 times less charges in the case of DMPE layers. The effect of these charges which is negligible at high salt concentration may significantly affect the adhesion energy and behaviour of neutral lipid bilayers between 0 and ≈ 40 salt. Content Type Journal Article Pages 127-130 DOI 10.1007/BF03219162 Authors F. Pincet, Laboratoire de Physique Statistique de l’École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France S. Cribier, Laboratoire de Physico-Chimie Moléculaire des Membranes Biologiques, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France E. Perez, Laboratoire de Physique Statistique de l’École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 1

Description:    Conservation equations are written for surface flows (either fluid or granular). The particularity of granular surface flows is then pointed out, namely that the depth of the flowing layer is not a priori fixed, leading to open equations. It is shown how some hypothesis on the flowing layer allows to close the system of equations. A possible hypothesis, similar to that made for a fluid layer, but inspired from granular flow experiments, is presented. The force acting on the flowing layer is discussed. Averaging over the flowing depth, as in shallow water theory, then allows to transform these conservation laws into equations for the evolution of the profile of a granular pile. Apart from their interest for building models, these conservation laws can be used to measure experimentally the effective forces acting on a flowing layer. Content Type Journal Article Pages 131-142 DOI 10.1007/BF03219163 Authors S. Douady, L.P.S./E.N.S., 25 rue Lhomond, 75242 Paris Cedex 05, France B. Andreotti, L.P.S./E.N.S., 25 rue Lhomond, 75242 Paris Cedex 05, France A. Daerr, L.P.S./E.N.S., 25 rue Lhomond, 75242 Paris Cedex 05, France Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 1

Description:    Multifractal critical phenomena with infinite-temperature critical point and with complex coexistence of the infinite and finite temperature critical points are considered and it is shown that strange attractors generated by cascades of period-doubling bifurcations (Feigenbaum scenario) as well as fields of velocity differences in fluid turbulence belong to the former subclass of the multifractal critical phenomena, while the real traffic processes and real currency exchange processes belong to the last (complex) subclass of the multifractal critical phenomena. Data obtained by different authors are used for this purpose. Content Type Journal Article Pages 361-364 DOI 10.1007/BF03219174 Authors A. Bershadskii, Ramat-Aviv, P.O. Box 39953, 61398 Tel-Aviv, Israel Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 2

Description:    The spin magnetic susceptibility of the p-d model is calculated by means of a perturbation theory in the hybridization term V through a generalized cumulant expansion (GCE). The analysis is approached from the paramagnetic metallic phase. The results qualitatively reproduce some unusual magnetic properties in the normal state of the hole-doped cuprates, supporting the scenario of a Van Hove singularity near the Fermi level. Content Type Journal Article Pages 235-242 DOI 10.1007/BF03219167 Authors R. Citro, Dipartimento di Scienze Fisiche “E.R. Caianiello”, Università di Salerno, 84081 Baronissi (Salerno), Italy M. Marinaro, Dipartimento di Scienze Fisiche “E.R. Caianiello”, Università di Salerno, 84081 Baronissi (Salerno), Italy Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 2

Description:    A phenomenological Landau elasticity for the shape, dilation, and lipid-tilt of bilayer membranes is developed. The shape mode couples with the sum of the monolayers’ tilt, while the dilation mode couples with the difference of the monolayers’ tilts. Interactions among membrane inclusions within regular arrays are discussed. Inclusions modifying the membrane thickness and/or inducing a tilt-difference due to their convex or concave shape yield a dilation-induced attraction and a tilt-difference-induced repulsion. The resulting interaction can stabilize 2 D crystal phases, with the possible coexistence of different lattice spacings when the dilation-tilt-difference coupling is large. Inclusions favoring crystals are those with either a long-convex or a short-concave hydrophobic core. Inclusions inducing a local membrane curvature due to their conical shape repel one another. At short inclusions separations, a tilt comparable with the inclusion’s cone angle develops: it relaxes the membrane curvature and reduces the repulsion. At large separations the tilt vanishes, whatever the value of the shape-tilt coupling. Content Type Journal Article Pages 261-272 DOI 10.1007/BF03219168 Authors J. -B. Fournier, Laboratoire de Physico-Chimie Théorique, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 2

Description:    Dissipative one-dimensional maps may exhibit special points ( e.g. , chaos threshold) at which the Lyapunov exponent vanishes. Consistently, the sensitivity to the initial conditions has a power-law time dependence, instead of the usual exponential one. The associated exponent can be identified with 1/(1 Ȣ q ), where q characterizes the nonextensivity of a generalized entropic form currently used to extend standard, Boltzmann-Gibbs statistical mechanics in order to cover a variety of anomalous situations. It has been recently proposed (Lyra and Tsallis, Phys. Rev. Lett. 80 , 53 (1998)) for such maps the scaling law 1/(1 − q ) = 1/ α min − 1/ α max , where α min and α max are the extreme values appearing in the multifractal f ( α ) function. We generalize herein the usual circular map by considering inflexions of arbitrary power z , and verify that the scaling law holds for a large range of z . Since, for this family of maps, the Hausdorff dimension d f equals unity for all z in contrast with q which does depend on z , it becomes clear that d f plays no major role in the sensitivity to the initial conditions. Content Type Journal Article Pages 309-315 DOI 10.1007/BF03219171 Authors U. Tırnaklı, Department of Physics, Faculty of Science, Ege University, 35100 Izmir, Turkey C. Tsallis, Centro Brasileiro de Pesquisas Fisicas, Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro - RJ, Brazil M. L. Lyra, Departamento de Fisica, Universidade Federal de Alagoas, 57072-970 Maceio-AL, Brazil Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 2

Description:    We study the influence of an aperiodic extended surface perturbation on the surface critical behaviour of the two-dimensional Ising model in the extreme anisotropic limit. The perturbation decays as a power κ of the distance l from the free surface with an oscillating amplitude where f l = 0, 1 follows some aperiodic sequence with an asymptotic density equal to 1/2 so that the mean amplitude vanishes. The relevance of the perturbation is discussed by combining scaling arguments of Cordery and Burkhardt for the Hilhorst-van Leeuwen model and Luck for aperiodic perturbations. The relevance-irrelevance criterion involves the decay exponent κ , the wandering exponent ω which governs the fluctuation of the sequence and the bulk correlation length exponent ν . Analytical results are obtained for the surface magnetization which displays a rich variety of critical behaviours in the ( κ, ω )-plane. The results are checked through a numerical finite-size-scaling study. They show that second-order effects must be taken into account in the discussion of the relevance-irrelevance criterion. The scaling behaviours of the first gap and the surface energy are also discussed. Content Type Journal Article Pages 273-285 DOI 10.1007/BF03219169 Authors L. Turban, Laboratoire de Physique des Matériaux, Université Henri Poincaré, BP 239, 54506 Vandœuvre lès Nancy Cedex, France Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 2

Description:    Previous experimental and theoretical studies suggest that first-spike latency is an efficient information carrier and may contain more amounts of neural information than those of other spikes. Therefore, the biophysical mechanisms underlying the first-spike response latency are of considerable interest. Here we present a systematical investigation on the response latency dynamics of a single Hodgkin-Huxley neuron subject to both a suprathreshold periodic forcing and background activity. In contrast to most earlier works, we consider a biophysically realistic noise model which allows us to relate the synaptic background activity to unreliable synapses and latency. Our results show that first-spike latency of a neuron can be regulated via unreliable synapses. An intermediate level of successful synaptic transmission probability significantly increases both the latency and its jitter, indicating that the unreliable synaptic transmission constrains the signal detection ability of neurons. Furthermore, we demonstrate that the destructive influence of synaptic unreliability can be controlled by the input regime and by the excitatory coupling strength. Better tuning of these two factors could help the H-H neuron encode information more accurately in terms of the first-spike latency. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-30282-0 Authors M. Uzuntarla, Engineering Faculty, Department of Biomedical Engineering, Bulent Ecevit University, 67100 Zonguldak, Turkey M. Ozer, Engineering Faculty, Department of Electrical-Electronics Engineering, Bulent Ecevit University, 67100 Zonguldak, Turkey D. Q. Guo, Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu, 610054 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    The effects of random distribution of magnetic impurities with concentration x in a semiconductor alloy multilayer at a paramagnetic temperature are investigated by means of coherent potential approximation and tight-binding model. The change in the electronic states and the optical absorption spectrum with x is calculated for weak and strong exchange interactions between carrier spins and localized spin moments on magnetic ions. We find that the density of states and optical absorption are strongly layer-dependent due to the quantum size effects. The electronic and optical spectra are broadened due to the spin fluctuations of magnetic ions and in the case of strong exchange interaction, an energy gap appears in both spectra. Furthermore, the interior layers show higher contribution in the optical absorption of the system. The results can be helpful for magneto-optical devices at a paramagnetic temperature. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-30354-1 Authors L. Gharaee, Department of Physics, Payame Noor University, P.O. Box 19395-3697, Tehran, Iran A. Saffarzadeh, Department of Physics, Payame Noor University, P.O. Box 19395-3697, Tehran, Iran Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    We investigate magneto-transport properties of a θ shaped three-arm mesoscopic ring where the upper and lower sub-rings are threaded by Aharonov-Bohm fluxes φ 1 and φ 2 , respectively, within a non-interacting electron picture. A discrete lattice model is used to describe the quantum network in which two outer arms are subjected to binary alloy lattices while the middle arm contains identical atomic sites. It is observed that the presence of the middle arm provides localized states within the band of extended regions and lead to the possibility of switching action from a high conducting state to a low conducting one and vice versa. This behavior is justified by studying persistent current in the network. Both the total current and individual currents in three separate branches are computed by using second-quantized formalism and our idea can be utilized to study magnetic response in any complicated quantum network. The nature of localized eigenstates are also investigated from probability amplitudes at different sites of the quantum device. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-30163-6 Authors Srilekha Saha, Theoretical Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Sector-I, Block-AF, Bidhannagar, 700064 Kolkata, India Santanu K. Maiti, School of Chemistry, Tel Aviv University, Ramat-Aviv, 69978 Tel Aviv, Israel S. N. Karmakar, Theoretical Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Sector-I, Block-AF, Bidhannagar, 700064 Kolkata, India Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    Based on the transfer-matrix method, the spin transport properties through a graphene-based multi-barrier nanostructure with an exchange field and Rashba spin orbit coupling (SOC), have been investigated. It is found that if Rashba SOC equals to the exchange field, the multi-barrier nanostructure is an efficient way to achieve spin rotators and spin filters. In addition, it is also found that the shot noise of a spin state can be enhanced by electrostatic potential, and plateaus of the Fano factor is formed. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-30245-5 Authors Q.P. Wu, School of materials science and engineering, Nanchang University, Nanchang, 330031 P.R. China X.D. He, School of Measuring and Optical Engineering, Nanchang Hangkong University, Nanchang, 330063 P.R. China Z.F. Liu, School of materials science and engineering, Nanchang University, Nanchang, 330031 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description: .   Using the formalism of the biased random walk in random uncorrelated networks with arbitrary degree distributions, we develop theoretical approach to the critical packet generation rate in traffic based on routing strategy with local information. We explain microscopic origins of the transition from the flow to the jammed phase and discuss how the node neighbourhood topology affects the transport capacity in uncorrelated and correlated networks. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-30062-x Authors P. Fronczak, Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw, Poland Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 10

Description:    We study strain-controlled magnetization-reorientation processes in nickel thin film/piezoelectric actuator hybrid structures. To obtain a consistent picture of the connection between magnetic microstructure and magnetoresistance, we correlate simultaneously measured spatially resolved magneto-optical Kerr effect imaging and integral magnetotransport measurements at room temperature. Our results show that the magnetization predominantly reorients by coherent rotation as a function of the voltage applied to the hybrid, except for a narrow region around the coercive field for which the magnetization reorientation evolves via domain effects. This demonstrates that both magnetic-field and strain-driven magnetization reversal can be modeled in terms of a macrospin model. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-20675-4 Authors A. Brandlmaier, Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany M. Brasse, Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany S. Geprägs, Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany M. Weiler, Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany R. Gross, Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany S. T. B. Goennenwein, Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    Previous studies have shown that in the Bose-Einstein condensation (BEC), temperature is a key factor, i.e., the lower the temperature is, the easier to observe particle condensation. While in recent studies of particle condensation on complex networks, temperature is not involved. We here propose a model of networked traps with distributed potential depths to include the temperature into particle diffusion. Through three typical potential forms, we find that the particle distribution in equilibrium satisfies a super-linear relationship with the node degree k i . Specifically, it will become a power law when the potential energy E i takes the form E i = ln k i . Furthermore, we surprisingly reveal that there is an optimal temperature T o k for the accumulation/condensation of particles at each group of nodes with the same degree k and T o k increases with k until T o hub of the hub, in contrast to the monotonous relationship between temperature and condensation in BEC. The optimal T o k comes from the competition between the trapping from attractive interaction among particles and the fluctuation controlled by temperature. Numerical simulations have completely confirmed the theoretical predictions. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-20794-x Authors L. Liu, Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai, 200062 P.R. China Z. H. Liu, Institute of Theoretical Physics and Department of Physics, East China Normal University, Shanghai, 200062 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    The local spin polarisation (LSP) of electrons in two typical semiconductor nanowires under the modulation of Rashba spin-orbit interaction (SOI) is investigated theoretically. The influence of both the SOI- and structure-induced bound states on the LSP is taken into account via the spin-resolved lattice Green function method. It is discovered that high spin-density islands with alternative signs of polarisation are formed inside the nanowires due to the interaction between the bound states and the Rashba effective magnetic field. Further study shows that the spin-density islands caused by the structure-induced bound state exhibit a strong robustness against disorder. These findings may provide an efficient way to create local magnetic moments and store information in semiconductors. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-20849-0 Authors X. B. Xiao, School of Computer, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004 P.R. China F. Li, School of Computer, Jiangxi University of Traditional Chinese Medicine, Nanchang, 330004 P.R. China Y. G. Chen, Department of Physics, Tongji University, Shanghai, 200092 P.R. China N. H. Liu, Institute for Advanced Study, Nanchang University, Nanchang, 330031 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    Spin tunneling in molecular magnets controlled by dipole-dipole interactions (DDI) in the disordered state has been considered numerically on the basis of the microscopic model using the quantum mean-field approximation. In the actual case of a strong DDI, coherence of spin tunneling is completely lost and there is a slow relaxation of magnetization, described by t 3/4 at short times. Fast precessing nuclear spins, included in the model microscopically, only moderately speed up the relaxation. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-20835-6 Authors D. A. Garanin, Department of Physics and Astronomy, Lehman College, City University of New York, 250, Bedford Park Boulevard West, Bronx, 10468 New York, USA Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    Recent Monte Carlo simulations on the Kern and Frenkel model of a Janus fluid have revealed that in the vapour phase there is the formation of preferred clusters made up of a well-defined number of particles: the micelles and the vesicles. A cluster theory is developed to approximate the exact clustering properties stemming from the simulations. It is shown that the theory is able to reproduce the micellisation phenomenon. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1140/epjb/e2012-20820-1 Authors R. Fantoni, National Institute for Theoretical Physics (NITheP) and Institute of Theoretical Physics, Stellenbosch University, 7600 Stellenbosch, South Africa Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We study a disordered nonlinear Schrödinger equation with an additional relaxation process having a finite response time τ . Without the relaxation term, τ = 0, this model has been widely studied in the past and numerical simulations showed subdiffusive spreading of initially localized excitations. However, recently Caetano et al. [Eur. Phys. J. B 80 , 321 (2011)] found that by introducing a response time τ 〉 0, spreading is suppressed and any initially localized excitation will remain localized. Here, we explain the lack of subdiffusive spreading for τ 〉 0 by numerically analyzing the energy evolution. We find that in the presence of a relaxation process the energy drifts towards the band edge, which enforces the population of fewer and fewer localized modes and hence leads to re-localization. The explanation presented here relies on former findings by Mulansky et al. [Phys. Rev. E 80 , 056212 (2009)] on the energy dependence of thermalized states. Content Type Journal Article Category Regular Article Pages 1-3 DOI 10.1140/epjb/e2012-21040-5 Authors M. Mulansky, Department of Physics and Astronomy, Potsdam University, 14476 Potsdam, Germany A. S. Pikovsky, Department of Physics and Astronomy, Potsdam University, 14476 Potsdam, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We study the equilibration of an initial surface of conic shape that consists of concentric circular monolayers by Kinetic Monte Carlo (KMC) method. The kinetic processes of attachment and/or detachment of particles to/from steps, diffusion of particles on the surface, along a step or cluster edges are considered. The difference between an up hill and down hill motion of a particle at a step are taken into account through the Ehrlich-Schwoebel (ES) barrier. The height of the cone evolves as h (0) −  h ( t ) ~  t 1/ α where h (0) is the initial height of the surface and α is approximately 2. The ES barrier slows down the equilibration of the surface but the time dependence remains as given above. The exponent α depends neither on ES barrier nor on the temperature. The equilibration is found also to be independent of energy barrier to the motion of particles along the step edges. The number of particles in each layer except the top two circular layers is found to decrease as t 0.57 . Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-20790-2 Authors M. Esen, Department of Physics, Faculty of Arts and Sciences, Cukurova University, 01330 Adana, Turkey A. T. Tüzemen, Department of Science and Mathematics Education in Secondary Schools, Faculty of Education, Cumhuriyet University, 58140 Sivas, Turkey M. Ozdemir, Department of Physics, Faculty of Arts and Sciences, Cukurova University, 01330 Adana, Turkey Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    The 4 × 4 transfer matrix for the magneto-optical layer at oblique incidence is derived. With the help of the transfer matrix, the magneto-optical properties of one-dimensional conjugated magnetophotonic crystals (MPC) heterojunctions are studied. The results show that there exists a Tamm state localized at the interface between conjugated MPC. By coupling the Tamm states, high transmittance and large Faraday rotation angle can be obtained simultaneously in conjugated MPC multiple heterojunctions structure. It can be used to make novel mageto-optical device, promised to further application in optical information process. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-20770-6 Authors C. P. Yin, Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou, 510006 P.R. China T. B. Wang, State Key Laboratory of Optoelectronic Materials and Technologies, Zhongshan (Sun Yat-Sen) University, Guangzhou, 510275 P.R. China H. Z. Wang, State Key Laboratory of Optoelectronic Materials and Technologies, Zhongshan (Sun Yat-Sen) University, Guangzhou, 510275 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    The results of powder neutron diffraction, X-ray resonant and non-resonant scattering in Tb 0.95 Bi 0.05 MnO 3 demonstrate that substitution of Bi for Tb leads to partial suppression of intrinsic long-range magnetic order in the Tb sub-lattice, which transforms to correlated short-range order. The magnetic order in the Mn sub-lattice remains similar to that of TbMnO 3 . In the Bi-substituted sample an anomaly in the temperature dependencies of the unit cell parameters was detected at about 100 K. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-20693-2 Authors I. V. Golosovsky, St. Petersburg Nuclear Physics Institute, 188300 Gatchina, St. Petersburg, Russia A. A. Mukhin, General Physics Institute RAS, 119991 Moscow, Russia V. Yu. Ivanov, General Physics Institute RAS, 119991 Moscow, Russia S. B. Vakhrushev, A.F. Ioffe Physico-Technical Institute RAS, 194021 St. Petersburg, Russia E. I. Golovenchits, A.F. Ioffe Physico-Technical Institute RAS, 194021 St. Petersburg, Russia V. A. Sanina, A.F. Ioffe Physico-Technical Institute RAS, 194021 St. Petersburg, Russia J. -U. Hoffmann, Helmholtz-Zentrum Berlin fur Materialien und Energie, Glienicker Str. 100, 14109 Berlin, Germany R. Feyerherm, Helmholtz-Zentrum Berlin fur Materialien und Energie, Glienicker Str. 100, 14109 Berlin, Germany E. Dudzik, Helmholtz-Zentrum Berlin fur Materialien und Energie, Glienicker Str. 100, 14109 Berlin, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    This paper reviews the transition path theory (TPT) for activated events and summarizes a set of methods and algorithms to compute all relevant quantities of this theory: free energy, rate and mechanism of the event. We provide a set of examples to illustrate the applicability of the methods to problems in chemistry, biophysics and material science. Content Type Journal Article Category Colloquium Pages 1-19 DOI 10.1140/epjb/e2012-20366-2 Authors S. Bonella, Dipartimento di Fisica and CNISM, Università La Sapienza, P.le A. Moro 2, 00185 Rome, Italy S. Meloni, School of Physics, Room 302 EMSC-UCD, University College Dublin, Belfield, 4 Dublin, Ireland G. Ciccotti, Dipartimento di Fisica and CNISM, Università La Sapienza, P.le A. Moro 2, 00185 Rome, Italy Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    In a complex network, different groups of nodes may have existed for different amounts of time. To detect the evolutionary history of a network is of great importance. We present a spectral-analysis based method to address this fundamental question in network science. In particular, we find that there are complex networks in the real-world for which there is a positive correlation between the eigenvalue magnitude and node age. In situations where the network topology is unknown but short time series measured from nodes are available, we suggest to uncover the network topology at the present (or any given time of interest) by using compressive sensing and then perform the spectral analysis. Knowledge of ages of various groups of nodes can provide significant insights into the evolutionary process underpinning the network. It should be noted, however, that at the present the applicability of our method is limited to the networks for which information about the node age has been encoded gradually in the eigen-properties through evolution. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-21019-2 Authors G. -M. Zhu, NUS Graduate School for Integrative Sciences and Engineering, 117456 Singapore, Republic of Singapore H. J. Yang, Department of Physics and Center for Computational Science and Engineering, National University of Singapore, 117546 Singapore, Singapore R. Yang, School of Electrical, Computer, and Energy Engineering, Arizona State University, 85287, Tempe, AZ, USA J. Ren, NUS Graduate School for Integrative Sciences and Engineering, 117456 Singapore, Republic of Singapore B. Li, NUS Graduate School for Integrative Sciences and Engineering, 117456 Singapore, Republic of Singapore Y. -C. Lai, Department of Physics and Center for Computational Science and Engineering, National University of Singapore, 117546 Singapore, Singapore Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    In this paper, we intend to study the effect of variable mass on the binding energy. In this regard, we apply an analytic expression for position-dependent effective mass in a cubic quantum dot. Then, we obtain the binding energies of a shallow donor in the quantum dot of GaAs/Al x Ga 1− x As using a variational procedure within the effective mass approximation. Calculations are presented with a constant effective mass and position-dependent effective mass. It is found that (i) the binding energy decreases as the dot length increases in both the cases of constant and variable masses, (ii) an increase of binding energy is observed when the spatially varying mass is included, and (v) the binding energy shows complicated behavior when the position-dependent mass is included for the small dot size L  ≤ 130 Å. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-20435-6 Authors R. Khordad, Department of Physics, College of Sciences, Yasouj University, 75914-353 Yasouj, Iran Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    We study numerically the spreading of an initially localized wave packet in a one-dimensional uncorrelated disordered chain with a nonadiabatic electron-phonon interaction. The nonadiabatic electron-phonon coupling is taken into account in the time-dependent Schrödinger equation by a delayed cubic nonlinearity. In the adiabatic regime, Anderson localization is destroyed and a subdiffusive spreading of wave packet takes place by moderate nonlinearity. In the nonadiabatic regime, the dynamical behavior becomes obviously different. We find that short delay time suppresses delocalization strongly. However, large delay time gives a stronger exponent of spreading. An explanation of this delay induced effect is also discussed. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-20864-1 Authors Z. J. Zhang, Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing, 210046 P.R. China W. J. Li, Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing, 210046 P.R. China P. Q. Tong, Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing, 210046 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    A study of the likelihood of quantum breathers in a quantum Heisenberg spin system including a Dzyaloshinsky-Moriya interaction (DMI) is done through an extended Bose-Hubbard model while using the scheme of few body physics. The energy spectrum of the resulting Bose-Hubbard Hamiltonian, on a periodic one-dimensional lattice containing more than two quanta shows interesting detailed band structures. From a non degenerate, and a degenerate perturbation theory in addition to a numerical diagonalization, a careful investigation of these fine structures is set up. The attention is focussed on the effects of various interactions that are; the DMI, the Heisenberg in-plane ( X , Y ) as well as the out of plane exchange interaction on the energy spectrum of such a system. The outcome displays a possibility of an energy self-compensation in the system. We also computed the weight function of the eigenstates in direct space and in the space of normal modes. From a perturbation theory it is shown that the interaction between the quanta leads to an algebraic localization of the modified extended states in the normal-mode space of the non-interacting system that are coined quantum q-breathers excitations. Content Type Journal Article Category Regular Article Pages 1-15 DOI 10.1140/epjb/e2012-20707-1 Authors Z. I. Djoufack, Nonlinear Physics and Complex Systems Group, Département de Physique, École Normale Supérieure, Universitéde Yaoundé I, B.P. 47, Yaoundé, Cameroon A. Kenfack-Jiotsa, Nonlinear Physics and Complex Systems Group, Département de Physique, École Normale Supérieure, Universitéde Yaoundé I, B.P. 47, Yaoundé, Cameroon J. P. Nguenang, A.S. International Centre for Theoretical Physics, Strada Costiera 11, Trieste, Italy Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    Topological properties of a periodic condensed matter system are global features of its Brillouin zone (BZ). In contrast, the validity of effective low energy theories is usually limited to the vicinity of a high symmetry point in the BZ. We derive a general criterion under which the control parameter of a topological phase transition localizes the topological defect in an arbitrarily small neighbourhood of a single point in k -space upon approaching its critical value. Such a local phase transition is associated with a Dirac-like gap closing point, whereas a flat band transition is not localized in k -space. This mechanism and its limitations are illustrated with the help of experimentally relevant examples such as HgTe/CdTe quantum wells and bilayer graphene nanostructures. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-21057-8 Authors J. C. Budich, Institute for Theoretical Physics and Astrophysics, University of Würzburg, 97074 Würzburg, Germany B. Trauzettel, Institute for Theoretical Physics and Astrophysics, University of Würzburg, 97074 Würzburg, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We study systems of a few charged bosons contained within a strongly anisotropic harmonic trap. A detailed examination of the ground-state correlation properties of two-, three-, and four-particle systems is carried out within the framework of the single-mode approximation of the transverse components. The linear correlation entropy of the quasi-1D systems is discussed in dependence on the confinement anisotropy and compared with a strictly 1D limit. Only at weak interaction the correlation properties depend strongly on the anisotropy parameter. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-20964-x Authors P. Kościk, Institute of Physics, Jan Kochanowski University, ul. Świętokrzyska 15, 25-406 Kielce, Poland A. Okopińska, Institute of Physics, Jan Kochanowski University, ul. Świętokrzyska 15, 25-406 Kielce, Poland Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    The effect of Dresselhauss spin-orbit coupling on transport and thermodynamic properties of a non-interacting two-dimensional electron gas (2DEG) is investigated. The Hamiltonian used also includes a tilted magnetic field and a Rashba spin-orbit interaction. The Dresselhauss spin-orbit interaction, likewise the Rashba spin-orbit interaction, introduces a beating pattern in the conductivity tensor and in the magnetization along the field direction. A method to estimate the contribution of the Rashba and Dresselhauss interactions to the beating pattern is given using the periodicity of the beating patterns. Content Type Journal Article Category Regular Article Pages 1-9 DOI 10.1140/epjb/e2012-20649-6 Authors T. F. A. Alves, Departamento de Física, Universidade Federal do Piauí, Campus Ministro Petrônio Portela, 64049-550 Teresina, Piauí, Brasil A. C. A. Ramos, Universidade Federal do Ceará, Campus do Cariri, 63030-200 Juazeiro do Norte, Ceará, Brasil G. A. Farias, Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, 60455-760 Fortaleza, Ceará, Brasil R. N. Costa Filho, Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, 60455-760 Fortaleza, Ceará, Brasil N. S. Almeida, Departamento de Física, Universidade do Estado do Rio Grande do Norte, 50610-210 Mossoró, Rio Grande do Norte, Brasil Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    In the present work, we have investigated tunneling dynamics of superfluid Fermi gas in a double-well potential in deep BEC regime and in the unitarity regime by adjusting the scattering length or the interaction parameter y . The scattering length a sc or y could affect the quantum transition dramatically. At certain regime, the complete population transfer between two modes can be obtained. However, at some other regimes, the quantum transition can be completely blocked. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-20941-5 Authors Y. Ma, College of Physics and Electronic, Engineering and Joint Laboratory of Atomic and Molecular Physics of NWNU & IMP CAS, Northwest Normal University, Lanzhou, 730070 P.R. China C. L. Wang, College of Physics and Electronic, Engineering and Joint Laboratory of Atomic and Molecular Physics of NWNU & IMP CAS, Northwest Normal University, Lanzhou, 730070 P.R. China W. S. Duan, College of Physics and Electronic, Engineering and Joint Laboratory of Atomic and Molecular Physics of NWNU & IMP CAS, Northwest Normal University, Lanzhou, 730070 P.R. China J. A. Sun, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou, 730070 P.R. China L. Yang, College of Physics and Electronic, Engineering and Joint Laboratory of Atomic and Molecular Physics of NWNU & IMP CAS, Northwest Normal University, Lanzhou, 730070 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    We numerically study traffic flow, energy dissipation and social payoff in the Nagel-Schreckenberg model with a non-signalized intersection. In terms of game theory, we analyze dilemma game observed in some traffic states. There are four traffic phases: free-flow phase, phase-segregated 1, phase-segregated 2 and jammed phase in the case of v max 〉 1. In phase-segregated 1, maximum traffic flow corresponds to minimal energy dissipation. Dilemma game is observed at the phase-segregated 1 in the case of v max 〉 1, and phase segregation state when v max = 1. Theoretical analyses give an agreement with numerical results. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-20904-x Authors W. Zhang, Department of Physics, Fudan University, Shanghai, 200433 P.R. China W. Zhang, Department of Physics and Siyuan Laboratory, Jinan University, Guangzhou, 510632 P.R. China W. Chen, Department of Physics, Fudan University, Shanghai, 200433 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    We study a selection of Cu-containing magnetic quadruple perovskites (CaCu 3 Ti 4 O 12 LaCu 3 Fe 4 O 12 , and YCu 3 Co 4 O 12 ) by ab initio calculations, and show that Cu is in an effective divalent Cu(II)-like state or a trivalent Cu(III) state depending on the choice of octahedral cation. Based on the electronic structure, we also discuss the role of Mott and Zhang-Rice physics in this materials class. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-21067-6 Authors P. Alippi, CNR-ISM, Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via Salaria km 29.5 CP 10, 00016 Monterotondo Stazione, Italy Vincenzo Fiorentini, Dipartimento di Fisica, Università di Cagliari and CNR-IOM, UOS Cagliari, Cittadella Universitaria, 09042 Monserrato, CA, Italy Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    The core width and Peierls barrier and stress for Shockley partials in InP have been investigated using the improved P-N theory. The core width of 90° partial is about 1.6 times wider than that of 30° partial, and both of them are very narrow: core width ξ  〈 0.5 b . In calculating the Peierls barrier and stress, the contribution from stain energy ignored by classical P-N theory has been considered. The calculated results show that when the dislocation moves, both the misfit and strain energies change periodically. They cancel each other due to the same order but opposite phases. Accordingly, the Peierls barrier and stress calculated from improved P-N theory are much lower than those calculated from the classical P-N theory. The Peierls barrier for 90° and 30° partials obtained by us is respectively about  ~0.047 eV/Å and 0.044–0.075 eV/Å, the Peierls stress is respectively about 3.7–5.0 GPa and 4.2–6.9 GPa. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-20713-3 Authors H. L. Zhang, Kunming University of Science and Technology, Kunming, 650093 P.R. China C. J. Yuan, Kunming University of Science and Technology, Kunming, 650093 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We theoretically determine the probability distribution function of the net field of the random planar structure of dipoles which represent polarized particles. At small surface concentrations c of the point dipoles this distribution is expressed in terms of special functions. At the surface concentrations of the dipoles as high as 0.6 the dipolar field obey the Gaussian law. To obtain the distribution function within transitional region c 〈 0.6, we propose the method based on the cumulant expansion. We calculate the parameters of the distributions for some specific configurations of the dipoles. The distribution functions of the ordered ensembles of the dipoles at the low and moderate surface concentrations have asymmetric shape with respect to distribution medians. The distribution functions allow to calculate various physical parameters of two-dimensional interacting nanoparticle ensembles. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-30057-7 Authors A. V. Panov, Institute of Automation and Control Processes, Far East Branch of Russian Academy of Sciences, 5, Radio st., 690041 Vladivostok, Russia Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    The importance of adequately modeling credit risk has once again been highlighted in the recent financial crisis. Defaults tend to cluster around times of economic stress due to poor macro-economic conditions, but also by directly triggering each other through contagion. Although credit default swaps have radically altered the dynamics of contagion for more than a decade, models quantifying their impact on systemic risk are still missing. Here, we examine contagion through credit default swaps in a stylized economic network of corporates and financial institutions. We analyse such a system using a stochastic setting, which allows us to exploit limit theorems to exactly solve the contagion dynamics for the entire system. Our analysis shows that, by creating additional contagion channels, CDS can actually lead to greater instability of the entire network in times of economic stress. This is particularly pronounced when CDS are used by banks to expand their loan books (arguing that CDS would offload the additional risks from their balance sheets). Thus, even with complete hedging through CDS, a significant loan book expansion can lead to considerably enhanced probabilities for the occurrence of very large losses and very high default rates in the system. Our approach adds a new dimension to research on credit contagion, and could feed into a rational underpinning of an improved regulatory framework for credit derivatives. Content Type Journal Article Category Regular Article Pages 1-19 DOI 10.1140/epjb/e2012-20740-0 Authors S. Heise, Mathematics Department, King’s College London, Strand, WC2R 2LS, London, UK R. Kühn, Mathematics Department, King’s College London, Strand, WC2R 2LS, London, UK Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    In this paper we have formulated a simple theoretical model for the dynamics of the time-varying target leverage ratio of a firm under some assumptions based upon empirical observations. In our theoretical model the time evolution of the target leverage ratio of a firm can be derived self-consistently from a set of coupled Ito’s stochastic differential equations governing the leverage ratios of an ensemble of firms by the nonlinear Fokker-Planck equation approach. The theoretically derived time paths of the target leverage ratio bear great resemblance to those used in the time-dependent stationary-leverage (TDSL) model [Hui et al., Int. Rev. Financ. Analy. 15 , 220 (2006)]. Thus, our simple model is able to provide a theoretical foundation for the selected time paths of the target leverage ratio in the TDSL model. We also examine how the pace of the adjustment of a firm’s target ratio, the volatility of the leverage ratio and the current leverage ratio affect the dynamics of the time-varying target leverage ratio. Hence, with the proposed dynamics of the time-dependent target leverage ratio, the TDSL model can be readily applied to generate the default probabilities of individual firms and to assess the default risk of the firms. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-20781-3 Authors C. F. Lo, Institute of Theoretical Physics and Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, P.R. China C. H. Hui, Research Department, Hong Kong Monetary Authority and Hong Kong Institute for Monetary Research, 55/F, Two International Finance Centre, 8 Finance Street, Central, Hong Kong SAR, P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    Many recent models of trade dynamics use the simple idea of wealth exchanges among economic agents in order to obtain a stable or equilibrium distribution of wealth among the agents. In particular, a plain analogy compares the wealth in a society with the energy in a physical system, and the trade between agents to the energy exchange between molecules during collisions. In physical systems, the energy exchange among molecules leads to a state of equipartition of the energy and to an equilibrium situation where the entropy is a maximum. On the other hand, in a large class of exchange models, the system converges to a very unequal condensed state, where one or a few agents concentrate all the wealth of the society while the wide majority of agents shares zero or almost zero fraction of the wealth. So, in those economic systems a minimum entropy state is attained. We propose here an analytical model where we investigate the effects of a particular class of economic exchanges that minimize the entropy. By solving the model we discuss the conditions that can drive the system to a state of minimum entropy, as well as the mechanisms to recover a kind of equipartition of wealth. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-21036-1 Authors J. R. Iglesias, Instituto de Física, UFRGS, and Instituto Nacional de Ciência e Tecnologia de Sistemas Complexos, Caixa Postal 15051, 91501-970 Porto Alegre, RS, Brazil R. M. C. de Almeida, Instituto de Física, UFRGS, and Instituto Nacional de Ciência e Tecnologia de Sistemas Complexos, Caixa Postal 15051, 91501-970 Porto Alegre, RS, Brazil Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    The quantum Goos-Hänchen (GH) shift of an electron (massive Dirac fermion) at a potential step in bilayer graphene is investigated. We show that the GH shift depends on the step height, the kinetic energy of the electron and incident angle. It is found that the GH shift can be large (positive or negative) under the suitable conditions. Content Type Journal Article Category Regular Article Pages 1-4 DOI 10.1140/epjb/e2012-20729-7 Authors M. Cheng, Department of Physics and Electronic Information Engineering, Minjiang University, Fuzhou, 350108 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We propose a generalized framework for the study of voter models in complex networks at the heterogeneous mean-field (HMF) level that (i) yields a unified picture for existing copy/invasion processes and (ii) allows for the introduction of further heterogeneity through degree-selectivity rules. In the context of the HMF approximation, our model is capable of providing straightforward estimates for central quantities such as the exit probability and the consensus/fixation time, based on the statistical properties of the complex network alone. The HMF approach has the advantage of being readily applicable also in those cases in which exact solutions are difficult to work out. Finally, the unified formalism allows one to understand previously proposed voter-like processes as simple limits of the generalized model. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-20501-1 Authors P. Moretti, Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Campus Nord B4, 08034 Barcelona, Spain S. Y. Liu, State Key Lab. of Industrial Control Technology, Institute of Cyber-systems and Control, Zhejiang University, Hangzhou, 310027 P.R. China A. Baronchelli, Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Campus Nord B4, 08034 Barcelona, Spain R. Pastor-Satorras, Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Campus Nord B4, 08034 Barcelona, Spain Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    The global time delay is introduced into a bistable system driven by two noises and a periodic signal. The signal power amplification factor η is employed to characterise stochastic resonance (SR) of the system. Numerical simulation results indicate the following. (1) For a periodic signal with low frequency ( Ω ), the typical behaviour of the SR is lowered monotonically by increasing the delay time τ ; for moderate Ω , τ enhances the SR behaviour and then weakens it, with a critical value at which the SR is optimum. (2) Multiplicative noise intensity D and additive noise intensity α have different influences on the SR performance, viz D enhances the SR monotonically while α enforces the SR initially and then restrains it; (3) correlation intensity λ between the two noises always weakens the SR behaviour of the system. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-21053-0 Authors L. C. Du, Department of Physics, Yunnan University, Kunming, 650091 P.R. China D. C. Mei, Department of Physics, Yunnan University, Kunming, 650091 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    Influence of the partial substitution of paramagnetic Fe 3+ ions by diamagnetic Ga 3+ ions in the trigonal crystal GdFe 3 (BO 3 ) 4 on its optical and magnetic properties is studied and discussed in connection with problems common for all antiferromagnets containing 3 d 5 ions. Polarized optical absorption spectra and linear birefringence of GdFe 3 (BO 3 ) 4 and GdFe 2.1 Ga 0.9 (BO 3 ) 4 single crystals have been measured in the temperature range 85–293 K. Specific heat temperature dependence (2–300 K) and structure of GdFe 2.1 Ga 0.9 (BO 3 ) 4 crystal have been also studied. As a result of substitution of 30% Fe to Ga the Neel temperature diminishes from 38 till 16 K, the strong absorption band edge shifts on 860 cm -1 (0.11 eV) to higher energy and the d - d transitions intensity decreases substantially larger than the Fe concentration does. Strong absorption band edge is shown to be due to Mott-Hubbard transitions. Correlation between position of the strong absorption band edge and the Neel temperature of antiferromagnets has been revealed. Properties of the doubly forbidden d - d transitions in the studied crystals and in other antiferromagnets are explained within the framework of the model of the exchange-vibronic pair absorption, which is theoretically analyzed in detail. The model permitted us to determine the connection between parameters of d - d absorption bands (intensity, width and their temperature dependences), on the one hand, and the exchange, spin-orbit and electron-lattice interactions, on the other hand. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1140/epjb/e2012-20953-1 Authors A. V. Malakhovskii, L.V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation A. L. Sukhachev, L.V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation A. D. Vasil’ev, L.V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation A. A. Leont’ev, L.V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation A. V. Kartashev, L.V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation V. L. Temerov, L.V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation I. A. Gudim, L.V. Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    The lack of d -electron screening in the s -electron spill-out region at the surface of Ag nanoparticles increases the electron-electron interaction in this region compared to the bulk. Therefore when comparing the electron-electron interaction contribution to the thermalization time of nanoparticles of varying radius, smaller particles thermalize faster due to the increased surface to bulk ratio. One aspect which has not been addressed is the effect of the spatial distribution of charge at the surface of the nanoparticle. In this work it is shown that the size dependence of the thermalization time is very sensitive to the surface density profile. The electron thermalization time of conduction electrons in noble metal nanoparticles as a function of the radius is calculated. The sensitivity of the scattering rate to the spatial distribution of charge at the surface of the nanostructure is analyzed using several model surface profiles. The change in surface charge distribution via charging or coating of the nanospheres is shown to be a tool for control and probing of the ultra-fast electron-electron dynamics in metallic nanoparticles. Content Type Journal Article Category Regular Article Pages 1-4 DOI 10.1140/epjb/e2012-20949-9 Authors C. López-Bastidas, Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Apartado Postal No. 14, CP 22860, Ensenada B.C., México Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    Networks with bimodal degree distribution are most robust to targeted and random attacks. We present a model for constructing a network with bimodal degree distribution. The procedure adopted is to add nodes to the network with a probability p and delete the links between nodes with probability (1 − p ). We introduce an additional constraint in the process through an immunity score, which controls the dynamics of the growth process based on the feedback value of the last few time steps. This results in bimodal nature for the degree distribution. We study the standard quantities which characterize the networks, like average path length and clustering coefficient in the context of our growth process and show that the resultant network is in the small world family. It is interesting to note that bimodality in degree distribution is an emergent phenomenon. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-30074-6 Authors Abhijeet R. Sonawane, Indian Institute of Science Education and Research, 411021 Pune, India A. Bhattacharyay, Indian Institute of Science Education and Research, 411021 Pune, India M. S. Santhanam, Indian Institute of Science Education and Research, 411021 Pune, India G. Ambika, Indian Institute of Science Education and Research, 411021 Pune, India Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    The thermal activation of magnetization reversal in magnetic nanoparticles is controlled by the anisotropy-energy barrier. Using perturbation theory, exact diagonalization and stability analysis of the ferromagnetic spin- s Heisenberg model with coupling or single-site anisotropy, we study the effects of quantum fluctuations on the height of the energy barrier. Opposed to the classical case, there is no critical anisotropy strength discriminating between reversal via coherent rotation and via nucleation/domain-wall propagation. Quantum fluctuations are seen to lower the barrier depending on the anisotropy strength, dimensionality and system size and shape. In the weak-anisotropy limit, a macrospin model is shown to emerge as the effective low-energy theory where the microscopic spins are tightly aligned due to the ferromagnetic exchange. The calculation provides explicit expressions for the anisotropy parameter of the effective macrospin. We find a reduction of the anisotropy-energy barrier as compared to the classical high spin- s limit. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-20936-2 Authors M. Sayad, I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany D. Gütersloh, I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany M. Potthoff, I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    In this paper, we investigate the quantum transport of a double quantum dot coupled with a nanomechanical resonator at arbitrary strong electron-phonon coupling regimes. We employ the generalized quantum master equation to study full counting statistics of currents. We demonstrate the coherent phonon states method can be applied to decouple the electron-phonon interaction non-perturbatively. With the help of this non-perturbative treatment of electron-phonon couplings, we find that the phonon-assisted resonant tunneling emerges when the excess energy from the left quantum dot to the right one can excite integer number of phonons and multi-phonon excitations can enhance the transport in strong electron-phonon coupling regime. Moreover, we find that as the electron-phonon coupling increases, it first plays a constructive role to assist the transport, and then plays the role of scattering and strongly represses the transport. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-30027-1 Authors C. Wang, Department of Physics, Zhejiang University, Hangzhou, 310027 P.R. China J. Ren, Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, Singapore, 117546 Republic of Singapore B. W. Li, Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, Singapore, 117546 Republic of Singapore Q. H. Chen, Department of Physics, Zhejiang University, Hangzhou, 310027 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We investigate the effects of magnetic and electric fields on electron wavefunction interactions in single walled carbon nanotube bundles. The magnetoresistance measurements performed at 4.2 K and the dependence of the data upon the electric field reveal good agreement with weak localization theory. An electrical field conditioned characteristic length is associated to ohmic-non ohmic transition, observed below 85 K, in current voltage characteristics. This length results equal to the average bundles diameter just at T ≅ 85 K, indicating that 2D–3D crossover is responsible for the observed conductance transition. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-20635-0 Authors M. Salvato, Dipartimento di Fisica and MINAS Laboratory, Università di Roma “Tor Vergata”, 00133 Roma, Italy M. Lucci, Dipartimento di Fisica and MINAS Laboratory, Università di Roma “Tor Vergata”, 00133 Roma, Italy I. Ottaviani, Dipartimento di Fisica and MINAS Laboratory, Università di Roma “Tor Vergata”, 00133 Roma, Italy M. Cirillo, Dipartimento di Fisica and MINAS Laboratory, Università di Roma “Tor Vergata”, 00133 Roma, Italy S. Orlanducci, Dipartimento di Scienze e Tecnologie Chimiche and MINAS Laboratory, Università di Roma “Tor Vergata”, 00133 Roma, Italy F. Toschi, Dipartimento di Scienze e Tecnologie Chimiche and MINAS Laboratory, Università di Roma “Tor Vergata”, 00133 Roma, Italy M. L. Terranova, Dipartimento di Scienze e Tecnologie Chimiche and MINAS Laboratory, Università di Roma “Tor Vergata”, 00133 Roma, Italy Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We consider a simple model of spring-mass block placed over a constant velocity v rolling plate. The map of the dynamic is presented in the ( v,r ) space where r accounts for the possible variation of the periodic shape profile of the rolling carpet. In order to characterize each type of motion, we found that evaluating the area of the phase space trajectories is more relevant than attempting on one hand, to solve analytically the asymptotic behavior, or on the other hand, to obtain an equivalent of the entropy and the free energy. First-order transition reveals to be the characteristic route from one type of motion to another. Later, we investigate the influence of the classical TMD 1 and TLCD 2 on the dynamic of this mass. Moreover, we numerically study the effects of a modified TMD. Reduced order parameter provides a quick overview of the whole system than phase space representations and bifurcation diagrams. Comparison of performances in the ( v , r ) space is made. It reveals the efficiency of the modified TMD. It comes out that the new TMD we designed stabilizes the system better than the two above control systems. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1140/epjb/e2012-20616-3 Authors A. Kenfack-Jiotsa, Laboratoire de Mécanique, Département de Physique, Faculté des Sciences, Université de Yaoundé, B.P. 812, Yaoundé, Cameroon M. Motchongom-Tingue, Laboratoire de Mécanique, Département de Physique, Faculté des Sciences, Université de Yaoundé, B.P. 812, Yaoundé, Cameroon D. C. Tsobgni-Fozap, Laboratoire de Mécanique, Département de Physique, Faculté des Sciences, Université de Yaoundé, B.P. 812, Yaoundé, Cameroon T. C. Kofané, Laboratoire de Mécanique, Département de Physique, Faculté des Sciences, Université de Yaoundé, B.P. 812, Yaoundé, Cameroon Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    In this paper, we investigate the transport properties of electrons on the surface of topological insulators with tuneable external ferromagnetic barriers. It is confirmed that the transport properties of electrons can be greatly affected by the magnitude (or the direction) of the magnetisation and the gate voltage. Some electronically or magnetically controlled devices may be constructed based on our research. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-20544-2 Authors J. P. Zhang, School of Physics, Huazhong University of Science and Technology, Wuhan, 430074 P.R. China J. H. Yuan, School of Physics, Huazhong University of Science and Technology, Wuhan, 430074 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We investigate the electronic transport for an impurity-doped armchair-edge graphene nanoribbon (AGNR), with 7 or 8 dimer lines along zigzag direction, sandwiched between two normal leads. By using the standard nonequilibrium Green’s function technique, it is demonstrated that, the impurity influence on the transport properties for system with semiconducting 7-AGNR system is more sensitive than that for one with metallic 8-AGNR system in the vicinity of the impurity energy level. In particular, in the absence of impurity the density of states (DOS) and linear conductance G possess a small zero value interval for 7-AGNR system and a large nonzero plateau for 8-AGNR one, respectively. Interestingly, as impurity included the DOS and G show a single sharp resonant peak around the impurity energy level for 7-AGNR system due to resonant tunneling, while a small dip appears in the same position for 8-AGNR system due to the antiresonance states. Moreover, we have also inspected the behavior of the differential conductance upon varying the impurity concentration for the systems. The findings here may suggest it is more favorable to fabricate an electric switch with high on-off ratio by using an impurity-assisted semiconducting AGNR. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-21013-8 Authors B. L. Zhou, Department of Physics and Key Laboratory for Low-Dimensional Quantum Structures and Manipulation (Ministry of Education), Hunan Normal University, 410081 Changsha, P.R. China B. H. Zhou, Department of Physics, Shaoyang University, 422001 Shaoyang, P.R. China X. W. Chen, Department of Physics and Key Laboratory for Low-Dimensional Quantum Structures and Manipulation (Ministry of Education), Hunan Normal University, 410081 Changsha, P.R. China G. H. Zhou, Department of Physics and Key Laboratory for Low-Dimensional Quantum Structures and Manipulation (Ministry of Education), Hunan Normal University, 410081 Changsha, P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    The modulational instability and gap solitons are theoretically studied in the ferromagnetic films under a periodic magnetic field. By multiple scale expansion, the envelope soliton solutions are obtained naturally. Due to the periodic modulation of dispersion, the solitons may be pushed into the gap region. For the easy-axis magnetic film, the red-shift of frequency leads to a modulational instability in the bottom of band and generates a bright gap soliton. For the easy-plane case, the blue-shift leads to an instability in the top of band and a dark gap soliton emerges. The weak damping produces an attenuation factor and a small oscillation. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-30080-8 Authors P. B. He, College of Physics and Microelectronics Science, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, Hunan University, Changsha, 410082 P.R. China G. N. Gu, College of Physics and Microelectronics Science, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, Hunan University, Changsha, 410082 P.R. China A. L. Pan, College of Physics and Microelectronics Science, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, Hunan University, Changsha, 410082 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    We study the dynamic phase transitions (DPT), within a mean-field approach, in the kinetic spin-1 Blume-Capel model by using the Glauber-type stochastic dynamics. The nature of the transition is characterized by investigating the behavior of the thermal variation of the dynamic order parameter and the Lyapunov exponent. The phase diagram is constructed in the temperatures ( T ) and single-ion anisotropy amplitude ( D ) plane. Our results predict first-order transitions at low temperature and large anisotropy strengths, which correspond in the phase diagram to the existence of a nonequilibrium tricritical point (TCP). We compare our results with the equilibrium phase diagram. Content Type Journal Article Category Regular Article Pages 1-4 DOI 10.1140/epjb/e2012-21002-y Authors E. Costabile, Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM, Brazil O. R. Salmon, Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM, Brazil J. R. de Sousa, Departamento de Física, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM, Brazil Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    Accurate determination of mean first-passage times (MFPTs) between any two states of a complex network still attracts considerable attention. Appropriate methods should take into account the discrepancy in MFPTs when a random walker moves first from a source to a target and then in the opposite direction. In addition, it is desirable to allow fast evaluation of mean first-passage times when transition probabilities are allowed to vary over time. For our calculations we make use of Hill’s algorithm, which enables the exact calculation of MFPTs. As we show in this work, when given a fixed distance to travel, the calculation of a particular MFPT depends on the choice of source and target points and their relative position on a lattice. We also demonstrate, when the network contains a relatively low number of cycles, that this deterministic technique provides exact results much faster in comparison to the more standard, but computationally demanding, stochastic Monte Carlo simulation method, where only approximate results can be obtained that are highly dependent on the number of walkers. Therefore, our specific implementation of Hill’s algorithm should facilitate efficient and accurate computation of MFPTs on a variety of network topologies of practical interest to the broad scientific community. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1140/epjb/e2012-20760-8 Authors M. Torchala, Biomolecular Modelling Laboratory, Cancer Research UK London Research Institute, 44 Lincoln’s Inn Fields, WC2A 3LY London, UK P. Chelminiak, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland P. A. Bates, Biomolecular Modelling Laboratory, Cancer Research UK London Research Institute, 44 Lincoln’s Inn Fields, WC2A 3LY London, UK Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 4

Description:    The single bipolaron problem is examined in the context of the 1D Holstein-Hubbard model, emphasizing analogies and differences with respect to the complementary single polaron physics. The bipolaron band structure below the phonon threshold is revealed, showing a complex relationship between numerous excited bands as the adiabatic limit is approached. Light bipolarons with significant binding energy, the stability of large bipolarons, the small to large bipolaron crossover as a function of the Hubbard repulsion, as well as the bipolaron dissociation, are investigated in detail, disentangling adiabatic, nonadiabatic and lattice coarsening effects. It is emphasized that condensation of bipolarons occurs in the dilute limit only at very low temperatures. Content Type Journal Article Category Regular Article Pages 1-12 DOI 10.1140/epjb/e2012-21079-2 Authors O. S. Barišić, Institute of Physics, Bijenička c. 46, 10000 Zagreb, Croatia S. Barišić, Department of Physics, Faculty of Science, University of Zagreb, Bijenička c. 32, 10000 Zagreb, Croatia Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We compute the partition function of the Potts model with arbitrary values of q and temperature on some strip lattices. We consider strips of width L y  = 2, for three different lattices: square, diced and ‘shortest-path’ (to be defined in the text). We also get the exact solution for strips of the Kagome lattice for widths L y  = 2,3,4,5. As further examples we consider two lattices with different type of regular symmetry: a strip with alternating layers of width L y  = 3 and L y  =  m  + 2, and a strip with variable width. Finally we make some remarks on the Fisher zeros for the Kagome lattice and their large q -limit. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1140/epjb/e2012-10625-7 Authors P. D. Alvarez, Centro de Estudios Científicos (CECS), 5110466 Valdivia, Chile F. Canfora, Centro de Estudios Científicos (CECS), 5110466 Valdivia, Chile S. A. Reyes, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, 22 Santiago, Chile S. Riquelme, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, 22 Santiago, Chile Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We study the emergence of oscillatory self-sustained behavior in a nonequilibrium Nambu system that features an exchange between different kinetical and potential energy forms. To this end, we study the Yamaleev oscillator in a canonical-dissipative framework. The bifurcation diagram of the nonequilibrium Yamaleev oscillator is derived and different bifurcation routes that are leading to limit cycle dynamics and involve pitchfork and Hopf bifurcations are discussed. Finally, an analytical expression for the probability density of the stochastic nonequilibrium oscillator is derived and it is shown that the shape of the density function is consistent with the oscillator properties in the deterministic case. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-20720-4 Authors S. Mongkolsakulvong, Faculty of Science, Department of Physics, Kasetsart University, 10900 Bangkok, Thailand P. Chaikhan, Faculty of Science, Department of Physics, Kasetsart University, 10900 Bangkok, Thailand T. D. Frank, Center for the Ecological Study of Perception and Action, Department of Psychology, University of Connecticut, 406 Babbidge Road, Storrs, 06269 CT, USA Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    In this paper, three new algorithms are introduced in order to explore long memory in financial time series. They are based on a new concept of fractal dimension of a curve. A mathematical support is provided for each algorithm and its accuracy is tested for different length time series by Monte Carlo simulations. In particular, in the case of short length series, the introduced algorithms perform much better than the classical methods. Finally, an empirical application for some stock market indexes as well as some individual stocks is presented. Content Type Journal Article Category Regular Article Pages 1-13 DOI 10.1140/epjb/e2012-20803-2 Authors M. J. Sánchez-Granero, Area of Geometry and Topology, Faculty of Science, Universidad de Almería, 04120 Almería, Spain M. Fernández-Martínez, Area of Geometry and Topology, Faculty of Science, Universidad de Almería, 04120 Almería, Spain J. E. Trinidad-Segovia, Department of Accounting and Finance, Faculty of Economics and Business, Universidad de Almería, 04120 Almería, Spain Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    Large adiabatic polarons in anisotropic crystals in the presence of constant magnetic field have been studied within the Holstein molecular crystal model in the continuum approximation. It was shown that magnetic field directed along the symmetry axis induces transverse confinement which may stabilize large polarons. They represent localized (soliton-like) nonlinear structure uniformly propagating along the symmetry axis and rotating around it in the same time. Such objects exist in 3D lattice provided that coupling constant and magnetic field do not exceed certain critical values. In contrast with pure 1D systems existence of large polarons is possible in a quite wider region of the values of coupling constant which may attain considerably higher values than in the pure 1D media. Furthermore, polaron effective mass, depending on the intensity of the applied magnetic field, may be considerably lighter than that of the the pure 1D polarons for the same values of coupling constant. This is the most significant difference with respect to pure 1D systems in the absence of magnetic field and may have substantial impact on polaron transport properties. Content Type Journal Article Category Regular Article Pages 1-10 DOI 10.1140/epjb/e2012-20782-2 Authors Ž. Pržulj, “Vinča” Institute of Nuclear Sciences, Laboratory for Theoretical and Condensed matter physics-020, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia Z. Ivić, “Vinča” Institute of Nuclear Sciences, Laboratory for Theoretical and Condensed matter physics-020, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia D. Kapor, Department of Physics, Faculty of Science, University of Novi Sad, Trg Dositeja Obradovica 4, 21000 Novi Sad, Serbia J. Tekić, “Vinča” Institute of Nuclear Sciences, Laboratory for Theoretical and Condensed matter physics-020, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description: Erratum to: Magnetic and transport properties of transition-metal implanted ZnO single crystals Content Type Journal Article Category Erratum Pages 1-1 DOI 10.1140/epjb/e2012-30089-y Authors R. P. Borges, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal B. Ribeiro, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal A. R. G. Costa, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal C. Silva, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal R. C. da Silva, Laboratório de Feixe de Iões, Dep. Física, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém, Portugal G. Evans, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal A. P. Gonçalves, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal M. M. Cruz, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal M. Godinho, Centro de Física da Matéria Condensada da Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal U. Wahl, Laboratório de Feixe de Iões, Dep. Física, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém, Portugal Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 3

Description:    We study the correlations in the one-dimensional extended quantum compass model in a transverse magnetic field. By exactly solving the Hamiltonian, we find that the quantum correlation of the ground state of one-dimensional quantum compass model is vanishing. We show that quantum discord can not only locate the quantum critical points, but also discern the orders of phase transitions. Furthermore, entanglement quantified by concurrence is also compared. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-21046-y Authors W. L. You, School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    We study the effects of an artificial gauge field on the ground-state phases of the Bose-Hubbard model on a checkerboard superlattice in two dimensions, including the superfluid phase and the Mott and alternating Mott insulators. First, we discuss the single-particle Hofstadter problem, and show that the presence of a checkerboard superlattice gives rise to a magnetic flux-independent energy gap in the excitation spectrum. Then, we consider the many-particle problem, and derive an analytical mean-field expression for the superfluid-Mott and superfluid-alternating-Mott insulator phase transition boundaries. Finally, since the phase diagram of the Bose-Hubbard model on a checkerboard superlattice is in many ways similar to that of the extended Bose-Hubbard model, we comment on the effects of magnetic field on the latter model, and derive an analytical mean-field expression for the superfluid-insulator phase transition boundaries as well. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-20852-5 Authors M. Iskin, Department of Physics, Koç University, Rumelifeneri Yolu, 34450 Sariyer, Istanbul, Turkey Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    The two-dimensional (2D) continuous elastic energy model for isotropic tubes is reduced to a one-dimensional (1D) curvature elastic energy model strictly. This 1D model is in accordance with the Kirchhoff elastic rod theory. Neglecting the in-plane strain energy in this model, it is suitable to investigate the nature features of carbon nanotubes (CNTs) with large deformations and can also reduce to the string model in [Z.C. Ou-Yang et al., Phys. Rev. Lett. 76 , 4055 (1997)] when the deformation is small enough. For straight chiral shapes, this general model indicates that the difference of the chiral angle between two equilibrium states is about π /6, which is consistent with the lattice model. It also reveals that the helical shape has lower energy for per atom than the straight shape has in the same condition. By solving the corresponding equilibrium shape equations, the helical tube solution is in good agreement with the experimental result, and super helical shapes are obtained and we hope they can be found in future experiments. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-21061-0 Authors X. H. Zhou, Department of Mathematics and Physics, Fourth Military Medical University, Xi’an, 710032 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    We theoretically investigate the Rashba and Dresselhaus spin-orbit interaction in AlAs/GaAs/Al 0.3 Ga 0.7 As/AlAs step-quantum wells. The ratio of Rashba and Dresselhaus spin splitting can be effectively manipulated by the well width and step width in the absence of electric field and magnetic field. When the well width of the step-quantum well is wider than 10 nm, the total spin splitting, which contains the contribution of interface as well as linear and cubic Dresselhaus terms, is always the greatest when the width of GaAs layer equals to about 2 nm. When the well width is wider than 2 nm, two different step widths can meet the SU(2) symmetry conditions, the smaller one of them results in maximum spin relaxation time. We also predict the application of the step-quantum well in spintronic devices. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-20736-8 Authors Y. F. Hao, Physics Department, Zhejiang Normal University, Zhejiang, 321004 P.R. China Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 2

Description:    Following a recent proposal by Burrard-Lucas et al. [arXiv:1203.5046] we intercalated FeSe with Li in liquid ammonia. We report on the synthesis of new Li x Fe 2 Se 2 (NH 3 ) y phases as well as on their magnetic and superconducting properties. We suggest that the superconducting properties of these new hybride materials appear not to be influenced by the presence of electronically-innocent Li(NH 2 ) molecules. Indeed, high onset temperatures of 44 K and shielding fractions of almost 80% were only obtained in samples containing exclusively Li x (NH 3 ) y moieties acting simultaneously as electron donors and spacer units. The c -axis lattice parameter of the new intercalated phases is strongly enhanced when compared to the alkali-metal intercalated iron selenides A 1− x Fe 2− y Se 2 with A = K, Rb, Cs, Tl with T c = 32 K. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-30422-6 Authors E. -W. Scheidt, CPM, Institute of Physics, University of Augsburg, 86157 Augsburg, Germany V. R. Hathwar, CPM, Institute of Physics, University of Augsburg, 86157 Augsburg, Germany D. Schmitz, CPM, Institute of Physics, University of Augsburg, 86157 Augsburg, Germany A. Dunbar, CPM, Institute of Physics, University of Augsburg, 86157 Augsburg, Germany W. Scherer, CPM, Institute of Physics, University of Augsburg, 86157 Augsburg, Germany F. Mayr, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86159 Augsburg, Germany V. Tsurkan, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86159 Augsburg, Germany J. Deisenhofer, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86159 Augsburg, Germany A. Loidl, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86159 Augsburg, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    We present computational evidence of the possibility of fast, supersonic or subsonic, nearly loss-free transport of electrons bound to lattice solitons along crystallographic axes in two-dimensional anharmonic crystal lattices. Content Type Journal Article Category Regular Article Pages 1-8 DOI 10.1140/epjb/e2012-30276-x Authors A. P. Chetverikov, Instituto Pluridisciplinar, Universidad Complutense, Paseo Juan XXIII, 1, 28040 Madrid, Spain W. Ebeling, Instituto Pluridisciplinar, Universidad Complutense, Paseo Juan XXIII, 1, 28040 Madrid, Spain M. G. Velarde, Instituto Pluridisciplinar, Universidad Complutense, Paseo Juan XXIII, 1, 28040 Madrid, Spain Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    The transverse-field XY model in one dimension is a well-known spin model for which the ground state properties and excitation spectrum are known exactly. The model has an interesting phase diagram describing quantum phase transitions (QPTs) belonging to two different universality classes. These are the transverse-field Ising model and the XX model universality classes with both the models being special cases of the transverse-field XY model. In recent years, quantities related to quantum information theoretic measures like entanglement, quantum discord (QD) and fidelity have been shown to provide signatures of QPTs. Another interesting issue is that of decoherence to which a quantum system is subjected due to its interaction, represented by a quantum channel, with an environment. In this paper, we determine the dynamics of different types of correlations present in a quantum system, namely, the mutual information I ( ρ AB ), the classical correlations C ( ρ AB ) and the quantum correlations Q ( ρ AB ), as measured by the quantum discord, in a two-qubit state. The density matrix of this state is given by the nearest-neighbour reduced density matrix obtained from the ground state of the transverse-field XY model in 1d. We assume Markovian dynamics for the time-evolution due to system-environment interactions. The quantum channels considered include the bit-flip, bit-phase-flip and phase-flip channels. Two different types of dynamics are identified for the channels in one of which the quantum correlations are greater in magnitude than the classical correlations in a finite time interval. The origins of the different types of dynamics are further explained. For the different channels, appropriate quantities associated with the dynamics of the correlations are identified which provide signatures of QPTs. We also report results for further-neighbour two-qubit states and finite temperatures. Content Type Journal Article Category Regular Article Pages 1-11 DOI 10.1140/epjb/e2012-30108-1 Authors A. K. Pal, Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, 700009 Kolkata, India I. Bose, Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, 700009 Kolkata, India Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    CaF 2 crystals doped with various concentrations of PbF 2 (0.4, 0.5, 1 and 2 mol%) were grown in vacuum, in a shaped graphite furnace using the vertical Bridgman method. The optical absorption spectra reveal the four characteristic UV absorption bands (labeled A, B, C and D) of the Pb 2+ ions. As the PbF 2 concentration increases, the structure of the bands become clearly visible, that is characteristic for the ns 2 ions in various hosts. High intensity emission bands in the near UV spectral region have been observed. The dependence on the Pb 2+ concentration of the optical absorption and emission of the Pb 2+ :CaF 2 crystals were not reported before. Content Type Journal Article Category Regular Article Pages 1-7 DOI 10.1140/epjb/e2012-30433-3 Authors I. Nicoara, Faculty of Physics, West University of Timisoara, 300223 Timisoara, Romania M. Paraschiva, Faculty of Physics, West University of Timisoara, 300223 Timisoara, Romania M. Stef, Faculty of Physics, West University of Timisoara, 300223 Timisoara, Romania F. Stef, Faculty of Physics, West University of Timisoara, 300223 Timisoara, Romania Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    We consider the exactly solvable spin-1/2 XX chain with the three-spin interactions of the XZX + YZY and XZY − YZX types in an external (transverse) magnetic field. We calculate the entropy and examine the magnetocaloric effect for the quantum spin system. We discuss a relation between the cooling/heating efficiency and the ground-state phase diagram of the quantum spin model. We also compare ability to cool/heat in the vicinity of the quantum critical and triple points. Moreover, we examine the magnetocaloric effect for the spin-1/2 XX chain with three-spin interactions in a random (Lorentzian) transverse magnetic field. Content Type Journal Article Category Regular Article Pages 1-9 DOI 10.1140/epjb/e2012-30359-8 Authors M. Topilko, Institute for Condensed Matter Physics, National Academy of Sciences of Ukraine, 1 Svientsitskii Street, 79011 L’viv-11, Ukraine T. Krokhmalskii, Institute for Condensed Matter Physics, National Academy of Sciences of Ukraine, 1 Svientsitskii Street, 79011 L’viv-11, Ukraine O. Derzhko, Institute for Condensed Matter Physics, National Academy of Sciences of Ukraine, 1 Svientsitskii Street, 79011 L’viv-11, Ukraine V. Ohanyan, Department of Theoretical Physics, Yerevan State University, Al. Manoogian 1, 0025 Yerevan, Armenia Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    MaxEnt’s variational principle, in conjunction with Shannon’s logarithmic information measure, yields only exponential functional forms in straightforward fashion. In this communication we show how to overcome this limitation via the incorporation, into the variational process, of suitable dynamical information. As a consequence, we are able to formulate a somewhat generalized Shannonian maximum entropy approach which provides a unifying “thermodynamic-like” explanation for the scale-invariant phenomena observed in social contexts, as city-population distributions. We confirm the MaxEnt predictions by means of numerical experiments with random walkers, and compare them with some empirical data. Content Type Journal Article Category Regular Article Pages 1-6 DOI 10.1140/epjb/e2012-30313-x Authors A. Hernando, Laboratoire Collisions, Agrégats, Réactivité, IRSAMC, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 09, France A. Plastino, IFLP-CCT-CONICET, National University La Plata, C.C. 727, 1900 La Plata, Argentina Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 8

Description:    We present a heuristic, semiphenomenological model of the anomalous temperature ( T ) dependence of resistivity ρ xx recently observed experimentally in the quasi-one-dimensional (Q1D) organic conductors of the (TMTSF) 2 X family in moderately strong magnetic fields. We suggest that a Q1D conductor behaves like an insulator (d ρ xx /d T 〈 0), when its effective dimensionality is one, and like a metal (d ρ xx /d T 〉 0), when its effective dimensionality is greater than one. Applying a magnetic field reduces the effective dimensionality of the system and switches the temperature dependence of resistivity between the insulating and metallic laws depending on the magnitude and orientation of the magnetic field. We critically analyze whether various microscopic models suggested in literature can produce such a behavior and find that none of the models is fully satisfactory. In particular, we perform detailed analytical and numerical calculations within the scenario of magnetic-field-induced spin-density-wave precursor effect suggested by Gor’kov and find that the theoretical results do not agree with the experimental observations. Content Type Journal Article Pages 385-399 DOI 10.1007/BF03219175 Authors A. T. Zheleznyak, Department of Physics and Center for Superconductivity Research, University of Maryland, College Park, MD 20742-4111, USA V.M. Yakovenko, Department of Physics and Center for Superconductivity Research, University of Maryland, College Park, MD 20742-4111, USA Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 11 Journal Issue Volume 11, Number 3

Description:    We evolve an effective interatomic interaction potential with long range Coulomb interactions, Hafemeister and Flygare type short range overlap repulsion extended up to second neighbor ions and van der Waals interaction to discuss the pressure dependent first order phase transition, mechanical, elastic, and thermodynamical properties of NaCl-type (B1) to CsCl-type (B2) structure in lanthanum pnictides (LaY, Y = N, P, As, Sb, and Bi). Both charge transfer interactions and covalency effect apart from long range Coulomb are important in revealing the high-pressure structural phase transition, associated volume collapse, elastic and thermodynamical properties. By analyzing the aggregate elastic constants pressure (temperature) dependence, the rare earth lanthanum pnictides are mechanically stiffened as a consequence of bond compression and bond strengthening attributed to mechanical work hardening, thermally softening arose due to bond expansion and bond weakening due to lattice vibrations, brittle (ductile) nature at zero (increased) pressure and temperature dependent brittleness from room temperature to high temperatures. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of elastic and thermodynamical properties explicitly the mechanical stiffening, thermally softening, and brittle (ductile) nature of rare earth LaY (Y = N, P, As, Sb and Bi) pnictides and still awaits experimental confirmations. Content Type Journal Article Category Regular Article Pages 1-31 DOI 10.1140/epjb/e2012-21054-y Authors D. Varshney, School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, 452001 Indore, India S. Shriya, School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, 452001 Indore, India M. Varshney, Department of Physics, M. B. Khalsa College, 452002 Indore, India Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 7

Description:    We have prepared potassium intercalated 1,2;8,9-dibenzopentacene films under vacuum conditions. The evolution of the electronic excitation spectra upon potassium addition as measured using electron energy-loss spectroscopy clearly indicate the formation of particular doped phases with compositions K x dibenzopentacene ( x = 1, 2, 3). Moreover, the stability of these phases as a function of temperature has been explored. Finally, the electronic excitation spectra also give insight into the electronic ground state of the potassium doped 1,2;8,9-dibenzopentacene films. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-30247-3 Authors F. Roth, IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany A. König, IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany B. Mahns, IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany B. Büchner, IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany M. Knupfer, IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 7

Description:    Solubilization of single-walled carbon nanotubes (SWNTs) has been essential for the understanding of their physical properties. Ultrasonication followed by centrifugation has been generally used for the preparation of SWNT dispersion in presence of different surfactants or conjugated polymers. However, the experimental condition and procedure show lab-to-lab dissimilarities. In this study, we report on the preparation and optical characterization of SWNTs dispersed with poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO). The effects of several processing parameters are investigated, such as sonication time, polymer concentration and centrifugation speed. Optical spectroscopic techniques including absorption and photoluminescence in the near-infrared spectral regions are used for the evaluation of the different SWNT dispersions. The optimal parameters to obtain isolated SWNTs are identified. Content Type Journal Article Category Regular Article Pages 1-5 DOI 10.1140/epjb/e2012-30120-5 Authors J. Gao, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands R. Annema, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands M. A. Loi, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands Journal The European Physical Journal B - Condensed Matter and Complex Systems Online ISSN 1434-6036 Print ISSN 1434-6028 Journal Volume Volume 85 Journal Issue Volume 85, Number 7