Mitigating disorder-induced zero-energy states in weakly-coupled semiconductor-superconductor hybrid systems

TL;DR

This paper shows that weak coupling in superconductor-semiconductor hybrids reduces disorder-induced trivial zero-energy states, aiding the detection of topological superconductivity and Majorana states, with implications for device design.

Contribution

It demonstrates that weak coupling mitigates disorder effects in hybrid systems, providing a strategy to distinguish topological states from trivial zero-energy states.

Findings

Weak coupling reduces disorder-induced trivial zero-energy states.

Strong disorder in the semiconductor favors strong coupling regimes.

Topological phase remains robust with a large gap in weak coupling.

Abstract

Disorder has appeared as one of the main mechanisms to induce topologically trivial zero-energy states in superconductor-semiconductor systems, thereby challenging the detection of topological superconductivity and Majorana bound states. Here we demonstrate that, for disorder in any part of the system, the formation of disorder-induced trivial zero-energy states can to a large extent be mitigated by keeping the coupling between the semiconductor and superconductor weak. The only exception is strong disorder in the semiconductor, where instead the strong coupling regime is somewhat more robust against disorder. Furthermore, we find that the topological phase in this weak coupling regime is robust against disorder, with a large and well-defined topological gap which is highly beneficial for topological protection. Our work shows the advantages and disadvantages of weak and strong couplings under disorder, important for designing superconductor-semiconductor hybrid structures.