Nanometer scale mapping of the density of states in an inhomogeneous superconductor
T. Cren; D. Roditchev; W. Sacks; J. Klein; T. Cren; Groupe 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; D. Roditchev; Groupe 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; W. Sacks; Groupe 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; J. Klein; Groupe 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
Журнал:
EPL (Europhysics Letters)
Дата:
2001-04-01
Аннотация:
Using high-speed scanning tunneling spectroscopy (STS), we perform a full mapping of the quasiparticle density of states (DOS) in single crystals of Bi<sub>2 − x</sub>Pb<sub>x</sub>Sr<sub>2</sub>CaCu<sub>2</sub>0<sub>8 + δ</sub>. The measurements carried out at 5 K showed a complex spatial pattern of important variations of the local DOS on the nanometer scale. Superconducting areas, characterized by a well-pronounced superconducting gap, are coexisting with regions of a peakless gap structure which we attribute to the pseudogap. Within the large superconducting regions, the spectra reveal strong peak/dip/hump signatures, identical to the pristine Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>0<sub>8 + δ</sub> case. On the contrary, in very small superconducting regions this fine structure is attenuated. Such a behavior of the local DOS suggests that the peak/dip/hump fine structure is not only a consequence of the superconducting state, but is also directly related to the scale of the phase coherence. The role of Bi-Pb substitutional disorder is discussed.
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