Majoranas with a twist: Tunable Majorana zero modes in altermagnetic heterostructures

TL;DR

This paper explores how rotating a semiconducting wire on an altermagnet can induce topological phases and Majorana zero modes, offering a new method to manipulate these modes without in situ tuning.

Contribution

It introduces a novel heterostructure setup with a rotating wire on an altermagnet to control topological phases and Majorana modes, including angle-dependent gap conditions and symmetry constraints.

Findings

Rotation induces topological phase transitions.

Majorana zero modes can be pinned at topological invariant changes.

Curved wires realize spatially-dependent topological regions.

Abstract

Altermagnetism provides new routes to realize Majorana zero modes with vanishing net magnetization. We consider a recently proposed heterostructure consisting of a semiconducting wire on top of an altermagnet and with proximity-induced superconductivity. We demonstrate that rotating the wire serves as a tuning knob to induce the topological phase. For $d$-, $g$- and $i$-wave altermagnetic pairing, we derive angle-dependent topological gap-closing conditions. We derive symmetry constraints on angles where the induced altermagnetism must vanish, which we verify by explicit models. Our results imply that a bent or curved wire realizes a spatially-dependent topological invariant with Majorana zero modes pinned to positions where the topological invariant changes. This provides a new experimental set-up whereby a single wire can host both topologically trivial and nontrivial regimes without $in$ $situ$ tuning.