Trivial Andreev band mimicking topological bulk gap reopening in the non-local conductance of long Rashba nanowires

TL;DR

This paper demonstrates that trivial Andreev bands in Rashba nanowires can mimic topological signatures in conductance measurements, challenging the reliability of the topological gap protocol for identifying Majorana states.

Contribution

It introduces a minimal model showing how trivial Andreev bands can produce false topological signatures in non-local conductance, serving as a benchmark for the topological gap protocol.

Findings

Trivial Andreev bands can cause apparent bulk gap reopening signatures.

These signatures are unaffected by trivial zero-bias peaks in local conductance.

The model provides a way to test the topological gap protocol's reliability.

Abstract

We consider a one-dimensional Rashba nanowire in which multiple Andreev bound states in the bulk of the nanowire form an Andreev band. We show that, under certain circumstances, this trivial Andreev band can produce an apparent closing and reopening signature of the bulk band gap in the non-local conductance of the nanowire. Furthermore, we show that the existence of the trivial bulk reopening signature (BRS) in non-local conductance is essentially unaffected by the additional presence of trivial zero-bias peaks (ZBPs) in the local conductance at either end of the nanowire. The simultaneous occurrence of a trivial BRS and ZBPs mimics the basic features required to pass the so-called "topological gap protocol". Our results therefore provide a topologically trivial minimal model by which the applicability of this protocol can be benchmarked.