Nanometer scale mapping of the density of states in an inhomogeneous superconductor
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
Accepted: 22 January 2001
Using high-speed scanning tunneling spectroscopy (STS), we perform a full mapping of the quasiparticle density of states (DOS) in single crystals of BiPbSrCaCu0. 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 BiSrCaCu0 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.
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, 2001