Constraints on the quasiparticle density of states in high- <i>T</i> <sub>c</sub> superconductors
Tristan CrenGroupe de Physique des Solides, Universités Paris 7 et Paris 6 Unité Mixte de Recherche CNRS (UMR 75 88) 2 Place Jussieu, 75251 Paris Cedex 5, FranceDimitri RoditchevGroupe de Physique des Solides, Universités Paris 7 et Paris 6 Unité Mixte de Recherche CNRS (UMR 75 88) 2 Place Jussieu, 75251 Paris Cedex 5, FranceW. SacksGroupe de Physique des Solides, Universités Paris 7 et Paris 6 Unité Mixte de Recherche CNRS (UMR 75 88) 2 Place Jussieu, 75251 Paris Cedex 5, FranceJ. KleinGroupe de Physique des Solides, Universités Paris 7 et Paris 6 Unité Mixte de Recherche CNRS (UMR 75 88) 2 Place Jussieu, 75251 Paris Cedex 5, France
2000en
ABI
Annotatsiya
In this Letter we present new tunneling data on YBa$_2$Cu$_3$O$_7$ thin films by low temperature scanning tunneling spectroscopy. Unusual peak-dip-hump features, previously reported in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, are also found in YBa$_2$Cu$_3$O$_7$. 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.
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