Constraints on the quasiparticle density of states in high-Tc superconductors
Groupe de Physique des Solides, Universités Paris 7 et
Unité Mixte de Recherche CNRS (UMR 75 88)
2 Place Jussieu, 75251 Paris Cedex 5, France
Accepted: 25 August 2000
In this letter we present new tunneling data on YBa2Cu3O7 thin films by low-temperature scanning tunneling spectroscopy. Unusual peak-dip-hump features, previously reported in Bi2Sr2CaCu2O, are also found in YBa2Cu3O7. To analyse these common signatures, we propose a new heuristic model in which, in addition to the d-wave symmetry, the gap function is energy dependent. A simple expression for the quasiparticle density of states is derived, giving an excellent agreement with the experiment. The dynamics of the quasiparticle states and the energy scales involved in the superconducting transition are discussed.
PACS: 74.25.-q – Superconductivity: General properties; correlations between physical properties in normal and superconducting states / 61.16.Ch – Scanning probe microscopy: scanning tunneling, atomic force, scanning optical, magnetic force, etc / 74.76.Bz – High-Tc films
© EDP Sciences, 2000