Disorder-induced topological transitions in multichannel Majorana wires

TL;DR

This paper studies how disorder affects topological phase transitions in multichannel Majorana nanowires, revealing that transport gap changes can induce topological shifts even with nonzero density of states.

Contribution

It provides analytical formulas for disorder-induced topological transitions in Rashba nanowires and confirms results with tight-binding simulations.

Findings

Transport gaps can induce topological transitions.

Disorder can change a wire's topological state.

Analytical formulas match numerical simulations.

Abstract

In this work, we investigate the effect of disorder on the topological properties of multichannel superconductor nanowires. While the standard expectation is that the spectral gap is closed and opened at transitions that change the topological index of the wire, we show that the closing and opening of a transport gap can also cause topological transitions, even in the presence of nonzero density of states across the transition. Such transport gaps induced by disorder can change the topological index, driving a topologically trivial wire into a nontrivial state or vice versa. We focus on the Rashba spin-orbit coupled semiconductor nanowires in proximity to a conventional superconductor, which is an experimentally relevant system, and obtain analytical formulas for topological transitions in these wires, valid for generic realizations of disorder. Full tight-binding simulations show excellent agreement with our analytical results without any fitting parameters.