Strain-controlled crossover between Majorana and Andreev bound states in disordered superconductor-semiconductor heterostructures

TL;DR

This paper demonstrates that applying spatially nonuniform strain in superconductor-semiconductor heterostructures can control and convert low-energy states, aiding the identification and stabilization of Majorana bound states for quantum computing.

Contribution

It introduces a strain-based control method to distinguish and stabilize Majorana bound states in disordered hybrid systems, supported by simulations and analytical modeling.

Findings

Weak strain can reshape low-energy spectra and modify topological phase boundaries.

Strain enables controlled crossover between trivial states, psABSs, and MBSs.

Disorder-induced psABSs can be converted into robust MBSs through strain.

Abstract

The unambiguous identification of topological Majorana-bound states (MBSs) in superconducting hybrid systems is hindered by trivial low-energy excitations, especially partially separated Andreev bound states (psABSs), which can mimic Majorana signatures. Here we show that spatially nonuniform strain offers a systematic route to control and interconvert these low-energy states. Using tight-binding Bogoliubov--de Gennes simulations, we study one-dimensional semiconductor nanowires and graphene nanoribbons with superconductivity, Rashba spin-orbit coupling, Zeeman fields, and disorder. We find that even weak strain can qualitatively reshape the low-energy spectrum by modifying effective band parameters and redistributing wavefunction weight. In nanowires, strain tunes the spatial overlap of Majorana components and shifts the topological phase boundary, enabling controlled crossovers between trivial states, psABSs, and topological MBSs. In graphene nanoribbons, where multiband effects and edge states produce a dense, hybridized low-energy spectrum, strain suppresses subband mixing, lifts degeneracies, and stabilizes boundary-localized modes. In both platforms, we identify regimes where disorder-induced psABSs are converted into well-separated and robust MBSs through strain-enhanced nonlocality. We further develop an analytical framework based on a position-dependent topological mass and strain-driven domain-wall motion, which captures the physical mechanism of these crossovers and yields a real-space criterion for the emergence and stability of Majorana modes. Our results establish strain as an effective tuning parameter for distinguishing and stabilizing topological MBSs in realistic disordered systems, and suggest an experimentally relevant pathway toward improved control and identification of Majorana modes in complex hybrid structures relevant to topological quantum computation.