# Proximity effect and interface transparency in Al/InAs-nanowire/Al diffusive junctions

## TL;DR

This study explores how the proximity effect and interface transparency in Al/InAs nanowire junctions depend on carrier density, revealing a transition from highly transparent diffusive behavior to reduced transparency as carrier density decreases.

## Contribution

It provides a detailed experimental and theoretical analysis of the proximity effect in Al/InAs nanowire junctions, highlighting the impact of interface transparency modulated by carrier density.

## Key findings

- High transparency interfaces show proximity gaps close to Al gap
- Reduced carrier density lowers the proximity gap to about half of Al gap
- A shallow potential barrier model accurately reproduces experimental behavior

## Abstract

We investigate the proximity effect in InAs nanowire (NW) junctions with superconducting contacts made of Al. The carrier density in InAs is tuned by means of the back gate voltage $V_g$. At high positive $V_g$ the devices feature transport signatures characteristic of diffusive junctions with highly transparent interfaces - sizable excess current, re-entrant resistance effect and proximity gap values ($\Delta_N$) close to the Al gap ($\Delta_0$). At decreasing $V_g$, we observe a reduction of the proximity gap down to $\Delta_N\approx\Delta_0/2$ at NW conductances $\sim2e^2/h$, which is interpreted in terms of carrier density dependent reduction of the Al/InAs interface transparency. We demonstrate that the experimental behavior of $\Delta_N$ is closely reproduced by a model with shallow potential barrier at the Al/InAs interface.