Disorder Suppression in Topological Semiconductor-Superconductor Junctions

TL;DR

This paper investigates how disorder in a superconductor affects topological superconductivity, finding that disorder scattering is suppressed at semiconductor-superconductor interfaces, which supports robust topological states.

Contribution

It provides a scattering and random-matrix analysis showing disorder suppression in topological Josephson junctions, highlighting near perfect Andreev reflection as a signature.

Findings

Disorder scattering rate is suppressed by the ratio of Fermi momenta.

Near perfect Andreev reflection indicates clean proximity effect.

Results extend to semiconductor nanowires with similar classical estimates.

Abstract

Disorder in a proximitizing bulk superconductor can scatter quasiparticles in a putative topological superconductor and eventually destroy the topological superconducting state. We use a scattering approach and a random-matrix calculation to estimate the disorder scattering time in a topological Josephson junction. We find that the disorder scattering rate from the bulk of the superconductor, even in the strong coupling limit, is suppressed in the ratio of Fermi momenta between the semiconductor and superconductor. This suppression of disorder scattering is accompanied by near perfect Andreev reflection at such semiconductor/superconductor interfaces, which can be used as a signature of such clean proximity effect. We also find that these results can be understood by a semiclassical estimate of scattering. We discuss limits in other systems such as the semiconductor nanowire where disorder scattering is suppressed according to similar classical estimates.