Size-effects in the Density of States in NS and SNS junctions

TL;DR

This paper investigates how the size of NS and SNS junctions affects the local density of states, revealing size-dependent oscillations and spectral features, and confirms the validity of the Andreev approximation across different geometries.

Contribution

It provides a detailed analysis of size effects on the LDOS in NS and SNS junctions, including oscillations and spectral features, extending understanding of quasiparticle behavior in these systems.

Findings

Finite transverse size causes pronounced LDOS effects.

Fast oscillations and additional peaks are observed in LDOS.

Andreev approximation remains valid across studied geometries.

Abstract

The quasiparticle local density of states (LDOS) is studied in clean NS and SNS junctions with increasing transverse size, from quasi-one-dimensional to three-dimensional. It is shown that finite transverse dimensions are related to pronounced effects in the LDOS, such as fast oscillations superimposed on the quasiparticle interference oscillations (for NS) and additional peaks in the bound state spectrum in the subgap region (for SNS). Also, the validity of the Andreev approximation is discussed. It turns out to be an acceptable approximation in all situations tested.