Trivial Andreev Band Mimicking Topological Bulk Gap Reopening in the Nonlocal Conductance of Long Rashba Nanowires

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 nonlocal conductance of the nanowire. Furthermore, we show that the existence of the trivial bulk reopening signature in nonlocal conductance is essentially unaffected by the additional presence of trivial zero-bias peaks in the local conductance at either end of the nanowire. The simultaneous occurrence of a trivial bulk reopening signature and zero-bias peaks 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.

Automated summary

In this study, we investigate a one-dimensional Rashba nanowire with multiple Andreev bound states forming an Andreev band in the bulk. We demonstrate that, under certain conditions, this trivial Andreev band can exhibit a noticeable closing and reopening of the bulk band gap in the nonlocal conductance of the nanowire. Additionally, we find that the presence of trivial zero-bias peaks in the local conductance at the ends of the nanowire does not significantly affect the existence of the trivial bulk reopening signature. The coexistence of the trivial bulk reopening signature and zero-bias peaks mimics the essential characteristics required for the topological gap protocol, providing a topologically trivial minimal model for benchmarking the applicability of this protocol.