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Anomalous density of states in a metallic film in proximity with a superconductor

A. K. Gupta·L. Cretinon·N. Moussy·B. Pannetier·H. Courtois
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Abstract

We investigated the local electronic density of states in superconductor-normal metal (Nb-Au) bilayers using a very low temperature (60 mK) STM. High resolution tunneling spectra measured on the normal metal (Au) surface show a clear proximity effect with an energy gap of reduced amplitude compared to the bulk superconductor (Nb) gap. Within this mini-gap, the density of states does not reach zero and shows clear sub-gap features. We show that the experimental spectra cannot be described with the well-established Usadel equations from the quasi-classical theory.

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A. K. Gupta, L. Cretinon, N. Moussy, B. Pannetier, H. Courtois. 2003-12-04. Anomalous density of states in a metallic film in proximity with a superconductor. https://doi.org/10.1103/physrevb.69.104514

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