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Disordrered superconducting thin films

Published on 13 December 2018

In highly disordered thin films of TiN , we have measured spatial fluctuations of the superconductivity. Unexpectedly, only two types of areas have been observed: either fully superconducting areas with a BCS gap in agreement with the bulk critical temperature or normal areas displaying either a flat density of states around the Fermi level or a zero bias anomaly related to Coulomb interactions. Moreover, the evolution of this density of states between these two zones reflects an anomalous proximity effect .

STM image 400 nm x 400 nm. At low temperature (100mK), superconducting areas (yellow) and normal areas (orange) spontaneously appear on disordered TiN thin films.
Spatial evolution of the tunneling spectra between a superconducting area and a normal one along the blue line drawn on the STM picture.

Escoffier W, Chapelier C, Hadacek N and Villégier JC
Anomalous proximity effect in an inhomogeneous disordered superconductor.
Physical Review Letters, 2004, 93(21): 217005