# Proximity-induced gap in nanowires with a thin superconducting shell

## TL;DR

This paper investigates how disorder in a thin superconducting shell enhances the proximity-induced gap in a coupled normal metal nanowire, overcoming finite-size suppression effects.

## Contribution

It demonstrates that disorder significantly increases the induced gap, approaching the superconductor's gap, which is a novel insight into proximity effects in nanowires.

## Key findings

- Disorder enhances the induced gap in nanowires with thin superconducting shells.
- Finite-size effects suppress the gap in clean systems, but disorder mitigates this suppression.
- Energy band shifts occur due to coupling with the superconducting shell.

## Abstract

Coupling a normal metal wire to a superconductor induces an excitation gap in the normal metal. In the absence of disorder, the induced excitation gap is strongly suppressed by finite-size effects if the thickness of the superconductor is much smaller than the thickness of the normal metal and the superconducting coherence length. We show that the presence of disorder, either in the bulk or at the exposed surface of the superconductor, significantly enhances the magnitude of the induced gap, such that it approaches the superconducting gap in the limit of strong disorder. We also discuss the shift of energy bands inside the normal-metal wire as a result of the coupling to the superconducting shell.