Spatially resolved spectroscopy on a superconducting proximity structure

Abstract

We investigated the local density of states (LDOS) of a normal metal (N) in good electrical contact with a superconductor (S) as a function of the distance $x$ to the NS interface. The sample consists of a pattern of alternate stripes of Au and Nb made by UV-lithography. We used a low temperature scanning tunneling microscope to record simultaneously $dI/dV(V,x)$ curves and the topographic profile $z(x)$. Nearby the NS interface, all the spectra show a dip near the Fermi energy but depending on the geometry, different behaviours can be distinguished. First, when the characteristic size of the normal metal $L$ is much larger than the coherence length ${\xi }_N\simeq \sqrt{\hslash D_N/2\Delta }$, the spectral extension of the dip decreases from $\Delta$ at the NS interface to zero at distances $x\gg {\xi }_N$. Second, when $L$ is comparable to ${\xi }_N$ the apparent gap in the LDOS is space-independent and related to the Thouless energy.

4 pages, 4 figures

References in corpus (1)

• Spectral Features of the Proximity Effect

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