ALBERT

Description: Author(s): L. Lin, H. M. Zhang, M. F. Liu, Shoudong Shen, S. Zhou, D. Li, X. Wang, Z. B. Yan, Z. D. Zhang, Jun Zhao, Shuai Dong, and J.-M. Liu Hexagonal LuFe O 3 has drawn a lot of research attention due to its contentious room-temperature multiferroicity. Due to the instability of hexagonal phase in the bulk form, most experimental studies focused on LuFe O 3 thin films which can be stabilized by strain using proper substrates. Here we report… [Phys. Rev. B 93, 075146] Published Tue Feb 23, 2016

Description: Author(s): Wei Tang, Lei Chen, Wei Li, X. C. Xie, Hong-Hao Tu, and Lei Wang In addition to the celebrated Affleck-Ludwig entropy originating from the open boundaries of the path-integral manifold, recent research has shown that the entropy correction on nonorientable manifolds such as the Klein bottle is also a universal characterization of critical systems with an emergent conformal field theory (CFT). Here, the authors show that the Klein bottle entropy can be interpreted as a boundary effect by transforming the Klein bottle into an orientable manifold, whereby the Klein bottle entropy bears a resemblance to the Affleck-Ludwig entropy. The authors then propose a generic scheme to extract these universal boundary entropies from lattice models. Numerical results for the q -state Potts model are compared with the CFT predictions. [Phys. Rev. B 96, 115136] Published Tue Sep 19, 2017

Description: Author(s): Z.-Y. Li, X. Li, J.-G. Cheng, L. G. Marshall, X.-Y. Li, A. M. dos Santos, W.-G. Yang, J. J. Wu, J.-F. Lin, G. Henkelman, T. Okada, Y. Uwatoko, H. B. Cao, H. D. Zhou, J. B. Goodenough, and J.-S. Zhou All single-valent oxide spinels are insulators. The relatively small activation energy in the temperature dependence of resistivity in vanadate spinels led to the speculation that the spinels are near the crossover from localized to itinerant electronic behavior, and the crossover could be achieved … [Phys. Rev. B 94, 165159] Published Mon Oct 24, 2016

Description: Author(s): D. F. Shao (邵定夫), R. C. Xiao, W. J. Lu, H. Y. Lv, J. Y. Li, X. B. Zhu, and Y. P. Sun The transition-metal dichalcogenide 1 T − TaS 2 exhibits a rich set of charge-density-wave (CDW) orders. Recent investigations suggested that using light or an electric field can manipulate the commensurate CDW (CCDW) ground state. Such manipulations are considered to be determined by charge-carrier dop… [Phys. Rev. B 94, 125126] Published Wed Sep 14, 2016

Description: Author(s): Q. Fan, X. P. Shen, M. Y. Li, D. W. Shen, W. Li, X. M. Xie, Q. Q. Ge, Z. R. Ye, S. Y. Tan, X. H. Niu, B. P. Xie, and D. L. Feng We have studied the low-lying electronic structure of a new ThCr 2 Si 2 -type superconductor KNi 2 Se 2 with angle-resolved photoemission spectroscopy. Three bands intersect the Fermi level, forming complicated Fermi surface topology, which is sharply different from its isostructural superconductor K x Fe  2−... [Phys. Rev. B 91, 125113] Published Mon Mar 09, 2015

Description: The authors revealed several important eigen properties of the stabilizing solutions of the two H-infinity Riccati equations and their product. Among them, the most prominent one is that the spectral radius of the product of these two Riccati solutions is a continuous, nonincreasing, convex function of gamma in the domain of interest. Based on these properties, quadratically convergent algorithms are developed to compute the optimal H-infinity norm. Two examples are used to illustrate the algorithms.

Description: The authors investigated some properties of the solutions to H-infinity Riccati equations which play a key role in the state approach to H-infinity optimization problem. The structure of the gamma-domain for the Riccati solutions has been described. There are two kinds of lower bounds for the solutions to exist and to be positive semidefinite respectively. A quadratically convergent algorithm for computing the lower bound is discussed.

Description: A wide diversity of planetary surfaces in the solar system represent high priority targets for in situ compositional and contextual analysis as part of future missions. The planned mission portfolio will inform our knowledge of the chemistry at play on Mars, icy moons, comets, and primitive asteroids, which can lead to advances in our understanding of the interplay between inorganic and organic building blocks that led to the evolution of habitable environments on Earth and beyond. In many of these environments, the presence of water or aqueously altered mineralogy is an important indicator of habitable environments that are present or may have been present in the past. As a result, the search for complex organic chemistry that may imply the presence of a feedstock, if not an inventory of biosignatures, is naturally aligned with targeted analyses of water-rich surface materials. Here we describe the two-step laser mass spectrometry (L2MS) analytical technique that has seen broad application in the study of organics in meteoritic samples, now demonstrated to be compatible with an in situ investigation with technique improvements to target high priority planetary environments as part of a future scientific payload. An ultraviolet (UV) pulsed laser is used in previous and current embodiments of laser desorption/ionization mass spectrometry (LDMS) to produce ionized species traceable to the mineral and organic composition of a planetary surface sample. L2MS, an advanced technique in laser mass spectrometry, is selective to the aromatic organic fraction of a complex sample, which can provide additional sensitivity and confidence in the detection of specific compound structures. Use of a compact two-step laser mass spectrometer prototype has been previously reported to provide specificity to key aromatic species, such as PAHs, nucleobases, and certain amino acids. Recent improvements in this technique have focused on the interaction between the mineral matrix and the organic analyte. The majority of planetary targets of astrobiological interest are characterized by the presence of water or hydrated mineral phases. Water signatures can indicate a history of available liquid water that may have played an important role in the chemical environment of these planetary surfaces and subsurfaces. The studies we report here investigate the influence of water content on the detectability of organics by L2MS in planetary analog samples.

Description: Since the Viking Program, quadrupole mass spectrometer (QMS) instruments have been used to explore a wide survey of planetary targets in our solar system, including (from the inner to outer reaches): Venus (Pioneer); our moon (LADEE); Mars (Viking, Phoenix, and Mars Science Laboratory); and, Saturns largest moon Titan (Cassini-Huygens). More recently, however, ion trap mass spectrometer (ITMS) instruments have found a niche as smaller, versatile alternatives to traditional quadrupole mass analyzers, capable of in situ characterization of planetary environments and the search for organic matter. For example, whereas typical QMS systems are limited to a mass range up to 500 Da and normally require multiple RF frequencies and pressures of less than 10(exp -6) mbar for optimal operation, ITMS instruments commonly reach upwards of 1000 Da or more on a single RF frequency, and function in higher pressure environments up to 10(exp -3) mbar.