Crossover in the local density of states of mesoscopic superconductor/normal-metal/superconductor junctions

Abstract

Andreev levels deplete energy states above the superconductive gap, which leads to the peculiar nonmonotonous crossover in the local density of states of mesoscopic superconductor/normal-metal/superconductor junctions. This effect is especially pronounced in the case when the normal metal bridge length $L$ is small compared to the superconductive coherence length $\ensuremath{\xi}$. A remarkable property of the crossover function is that it vanishes not only at the proximity induced gap ${ϵ}_{g}$ but also at the superconductive gap $\ensuremath{\Delta}$. Analytical expressions for the density of states at both gap edges, as well as the general structure of the crossover are discussed.