Dependence of {ital T}{sub {ital c}} on the physical parameters in single-layered copper oxides

Journal Article · Sun Oct 01 04:00:00 EDT 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.52.10330· OSTI ID:239366

Hocquet, T ^[1]; Jardin, J ^[2]; Germain, P; Labbe, J ^[1]

---

1. Laboratoire de Physique de la Matiere Condensee de l`Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05 (France)
2. Laboratoire des Proprietes Mecaniques et Thermodynamiques des Materiaux (CNRS), Universite Paris Nord, 93430 Villetaneuse (France)

From the superconducting gap equation that we have derived in a previous paper, we calculate the critical superconducting temperature {ital T}{sub {ital c}} of an itinerant electron gas in a CuO{sub 2} plane as a function of the occupancy of the {ital d}-{ital p} subband. This involves applying the Bogoliubov-Valatin mean-field approximation to a Hamiltonian including both the Hubbard intra-atomic repulsion {ital U} and an effective coupling constant {ital V} between electrons; the latter is assumed to be mediated by the electron-phonon interaction. As the Fermi level is shifted from the logarithmic Van Hove singularity in the electronic density of states, the calculated value of {ital T}{sub {ital c}} decreases much more slowly than the antiferromagnetic order parameter that we had previously calculated in the same model. This explains the existence of the superconducting phase largely outside of the domain of stability of the antiferromagnetic phase, when the compound is doped. Furthermore, we calculate the isotope effect, which exhibits a large variation with the doping {ital x}, showing a sharp peak for some critical value of {ital x}, in agreement with several independent experimental data. A very large influence of the Coulomb parameter {ital U} is found on the isotope effect which, in some cases, could vanish, or even be negative.

• OSTI ID: 239366
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 14 Vol. 52; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ANTIFERROMAGNETISM
BOGOLYUBOV METHOD
COPPER OXIDES
ELECTRON-PHONON COUPLING
ENERGY GAP
ENERGY-LEVEL DENSITY
FERMI LEVEL
HIGH-TC SUPERCONDUCTORS
HUBBARD MODEL
ISOTOPE EFFECTS
MEAN-FIELD THEORY
ORDER PARAMETERS
TRANSITION TEMPERATURE