Scanning Tunneling Spectroscopy on a Disordered Superconductor.

Thin disordered TiN films display a multiple reentrant superconductor-insulator transition. By combining very low temperature scanning tunneling microscopy and spectroscopy on TiN films we have observed a non uniform state made of superconducting and normal areas. These inhomogeneities can be related to fluctuations driven quantum superconductor-metal transition models recently developed. When the disorder of the film is increased or its thickness reduced, electronic interactions begin to take over and the LDOS develops a zero bias anomaly (ZBA). We observed smooth spatial transitions between areas displaying a superconducting LDOS and other ones with a ZBA in the excitation spectrum. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]