Superconducting properties close to metal-insulator transition in disordered 3D-NbN films.

by Mintu Mondal (TIFR - Mumbai)

Wednesday 21 Apr 2010, 14:00 → 15:00 Europe/Rome

Conversi (Dipartimento di Fisica - Ed. G.Marconi)

I will present the evolution of superconducting properties in epitaxial homogeneously disordered 3D-NbN films close to the quantum critical point for the metal-insulator transition. The effective disorder in NbN is varied from moderately clean limit down to the Anderson metal-insulator transition, by controlling the deposition parameter. As we approach towards metal-insulator transition, the superconducting transition temperature decreases and we observe a coinciding metal-insulator and superconductor-insulator transition. In the lower disorder limit the superconducting energy gap and the magnetic penetration depth follow a BCS behavior. However, as we approach the metal-insulator transition, the superconductivity is characterized by the suppression of coherence peaks in the differential conductance spectra of planar tunnel junctions and by a linear temperature dependence of superfluid density. Our results indicate that close to the quantum critical point the elementary excitations are different than that of a conventional superconductor.