Proximity effect in a two-dimensional electron gas coupled to a thin superconducting layer

TL;DR

This paper investigates the proximity effect in a 2D electron gas coupled to a thin superconductor, revealing challenges in realizing topological phases due to band shifts and parameter renormalization.

Contribution

It demonstrates how the superconductor induces a large band shift and parameter renormalization, complicating the realization of topological phases in such heterostructures.

Findings

Large band shift induced by the superconductor.

Thicker superconducting layers reduce band shift but increase parameter renormalization.

Tuning into a topological phase remains challenging due to these effects.

Abstract

There have recently been several experiments studying induced superconductivity in semiconducting two-dimensional electron gases that are strongly coupled to thin superconducting layers, as well as probing possible topological phases supporting Majorana bound states in such setups. We show that a large band shift is induced in the semiconductor by the superconductor in this geometry, thus making it challenging to realize a topological phase. Additionally, we show that while increasing the thickness of the superconducting layer reduces the magnitude of the band shift, it also leads to a more significant renormalization of the semiconducting material parameters and does not reduce the challenge of tuning into a topological phase.