ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Artikel  (12)
  • High-temperature superconductivity  (12)
  • Springer  (12)
  • Nature Publishing Group
  • 2020-2020
  • 1995-1999  (12)
  • 1970-1974
  • 1945-1949
  • Elektrotechnik, Elektronik, Nachrichtentechnik  (12)
Sammlung
  • Artikel  (12)
Verlag/Herausgeber
  • Springer  (12)
  • Nature Publishing Group
Erscheinungszeitraum
  • 2020-2020
  • 1995-1999  (12)
  • 1970-1974
  • 1945-1949
  • 1990-1994  (13)
Jahr
Thema
  • Elektrotechnik, Elektronik, Nachrichtentechnik  (12)
  • Physik  (12)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 11 (1998), S. 769-774 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; two-dimensional Hubbard model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The interlayer tunneling in high-temperature superconductors has been reconsidered beyond the mean-field approximation. The modification of the quasiparticle spectrum originating from the momentum-conserving interlayer transportation of Cooper pairs has been taken into account exactly. The pronounced reduction of the superconducting transition temperature when compared to the mean-field solution can be observed. Our self-consistent Green's functions approach allows for incorporation of Coulomb correlation and gives support for the mixed s- and d-wave scenario of high-temperature superconductivity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 11 (1998), S. 667-671 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; two-dimensional Hubbard model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We have considered the problem of s-wave and d-wave superconductivity in the two-layer Hubbard model close to the metal-insulator transition. To mimic the formation of the insulating gap, the Coulomb correlations have been taken into account within the Hubbard I approximation. The interlayer momentum-conserving Josephson tunneling between the layers has been included on the mean-field level. We demonstrate that the interlayer tunneling may contribute to the occurrence of mixed d + s wave symmetry of the superconducting state with a dominating d-wave component at a low concentration of holes. The problem of the validity of the pair-tunneling model is also briefly discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 11 (1998), S. 239-244 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; pressure effect ; wave functions overlap ; dependence on doping ; impurity model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The model of the pressure effect on the critical temperature T c in high-temperature superconductors [11], earlier proposed by the present author and consisting in the increase of the pair wave function overlap with increase in pressure p that in its manifestations is equivalent to an increase in doping, is compared with the recent experimental data [1–4]. By making this model more precise for inhomogeneous specimens, we obtained the doping region near the optimal one where the critical temperature is independent of doping, and the pressure region where it is independent of pressure. It is shown that, as observed in [1,2], the dependence of dT c/dp on doping in HgBa2CuO4+δ after excluding the influence of the specimen's inhomogeneous structure is explained satisfactorily by the model of [11]. So the introduction in [1,2] of a term in T c proportional to p 2 is unnecessary. An analogous comparison is made for YBa2Cu3O6+y .
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 9 (1996), S. 81-87 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; two-dimensional Hubbard model ; Eliashberg equations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We discuss the impact of the strong electron-phonon interactions on the physical properties of correlated electrons in the two-dimensional Hubbard model. An easy access to the physical properties of the superconducting state is obtained by solving the Eliashberg equations with explicit momentum-dependent kernels. In order to facilitate the numerical procedure to solve these equations, correlations are treated within the Gutzwiller approximation (i.e., mean-field-slave boson approximation). Our results strongly support the view thatd-wave symmetry is the most important feature of the superconducting state in the copper oxides. A possible extension beyond the mean field approximation is also presented.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 9 (1996), S. 113-119 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; Fermi liquid ; layered structure ; disordered magnetic correlations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract Using the Eliashberg equations for superconductivity in a layered high-temperature superconductor and taking into consideration the phonon-mediated electron-electron interaction and the effect of the disordered magnetic correlations, we calculated the expressions for the critical temperature. The phonon and the magnetic kernels have a logarithmic divergence in the lowfrequency limit and the critical temperature differs from the McMillan form. The effect of various parameters on the decrease of the critical temperature has been analyzed. The renormalization functionZ ph (ω) contains a logarithmic dependence onω.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 11 (1998), S. 677-682 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; ferrons ; barrier
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We study the behavior of an extra hole added to the ground state of the antiferromagnetically ordered CuO2 plane. Both the Cu--O hybridization and the O--O transfer are taken into account. As has been shown previously (V. Hizhnyakov and E. Sigmund, Physica C 156, 655 [1988]), the energetically most favorable situation is given when a localized state is formed in which the antiferromagnetic order is locally destroyed and a small ferromagnetic cluster is built up. We show that due to the increase of the magnetic energy induced by the spin–flip process (E s∼0.15 eV), the localized and the metastable free-hole states are separated by a barrier of energy (E b∼0.05 eV), which can reveal itself in various kinetic phenomena.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 12 (1999), S. 649-654 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; two-dimensional Hubbard model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We considered anisotropic superconductivity within the two-dimensional Hubbard model extended by pairing correlations originating from the electron–phonon interaction. To discuss the onset of superconductivity close to the insulator–metal transition, we used the Hubbard I approximation to account for the formation of the insulating gap and see the role of Coulomb correlations for superconducting pairing. It has been shown that the Hubbard I approximation reflects effective pairing interactions genuine for correlated electron systems and leads to the stabilization of the superconductivity in the d-wave channel. One may expect the cooperation of phonon-free and phonon-induced mechanism in the formation of thed-wave superconducting state.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 8 (1995), S. 227-231 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; superconducting dual-mode resonator ; superconducting thin film ; superconducting microwave device ; pulsed laser deposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We report, for the first time to our knowledge, a clear resonant peak split in the range of 7.7–9.7 GHz in a perturbed dual-mode disk-type resonator (DMDR) made of YBa2Cu3O7−x (YBCO) superconducting thin film on MgO substrate. Epitaxial YBCO superconducting thin films were grown on (100) MgO substrates by pulsed laser deposition technique. The critical temperature of superconducting thin film on MgO substrate was 85 K. Superconducting dualmode disk resonators were designed by microwave design software, EEsof, and patterned by photolithography and a wet-etch process. The unloaded quality factor (QUL) of the superconducting DMDR was found to be 1,312 at 77 K. We believe this type of DMDR can be utilized for dual-mode resonator-based filters for satellite communications.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 8 (1995), S. 135-141 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; two-dimensional Hubbard model ; Eliashberg equations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We address the problem of anisotropic superconductivity in the two-dimensional Hubbard model. The Eliashberg equations have been generalized to the case which accounts for the anisotropy of the order parameter. Strong local correlations are treated within the mean field slave boson approximation. The superconducting transition temperatureT c is evaluated as a function of the occupation number. Our results indicate that thed-wave state is the most likely channel for superconductivity for small concentration of holes. We have also derived an approximate analytical formula forT c valid for any value of the occupation number. In addition, the influence of strong correlations on the electron-phonon coupling function is also discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 9 (1996), S. 33-42 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; impurity mechanism ; localization ; percolation threshold ; irreversibility line ; Meissner fraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The impurity mechanism proposed earlier is used to interpret the magnetic properties of hightemperature superconductors. The appearance of superconductive granules and the existence of weak bonds in grains of ceramics and in single crystals is explained. The irreversibility line is obtained and its new interpretation as the line of thresholds of appearance of infinite nonsuperconductive cluster is given. The relaxation time of the magnetic susceptibility in alternating magnetic fields is calculated. The decrease of the Meissner fraction with increase in magnetic field and decrease in doping, and other magnetic properties are explained.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 9 (1996), S. 373-378 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; photoemission spectroscopy ; electronic structure ; pairing symmetry ; Fermi surface
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We continue to study Bi2Sr2CaCu2O8+δ with angle-resolved photoemission spectroscopy, in order to gain detailed knowledge of the high-temperature superconductors' electronic structure. While the photoemission community has already established some important general characteristics of this material, continued investigation reveals a rich variety of details. In the superconducting state, we have looked for details in the gap anisotropy. In the normal state, we have concentrated on the evolution of the Fermi surface as the carrier doping is reduced.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of superconductivity 9 (1996), S. 571-578 
    ISSN: 1572-9605
    Schlagwort(e): High-temperature superconductivity ; two-dimensional Hubbard model ; Eliashberg equation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We consider the two-dimensional Hubbard model including electron-phonon interaction. Strong local correlations (U→∞ limit) are taken into account within the mean-field approximation for auxiliary boson fields. Phonon-assisted transitions between intraand interlayer states are introduced as the source of coupling between two-dimensional CuO2 layers. This type of processes effectively leads to the nonlinear (quadratic) interaction of intralayer electrons withc-axis phonons. We construct the Eliashberg equations for the resulting Hamiltonian and evaluate the superconducting transition temperatureT c. Our model calculation demonstrates that a pronounced enhancement ofT c in thed-wave channel is possible. The largest enhancement ofT c tends to take place for small hole concentrations. This means that the coupling toc-axis phonons could compete with two-dimensional correlations responsible for the onset of antiferromagnetic order. It is remarkable that the two-dimensional features in the normal state are hardly affected by this specific interlayer interaction. Therefore,c-axis two-phonon-mediated interlayer coupling can cooperate with interlayer pair tunneling and substantially contribute to an increased pairing.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...