Magnetoelectric effects in superconducting nanowires with Rashba spin-orbit coupling

TL;DR

This paper predicts novel magnetoelectric effects in superconducting nanowires with Rashba spin-orbit coupling, including equilibrium currents and charge pumping, which serve as signatures of the topological phase transition and Majorana states.

Contribution

It introduces the prediction of unconventional magnetoelectric effects in nanowires with Rashba coupling, highlighting their behavior at the topological phase transition.

Findings

Magnetic fields parallel to the spin-orbit axis induce equilibrium currents.

Perpendicular magnetic fields can cause charge pumping.

Magnetoelectric effects signal the topological phase transition.

Abstract

Recent experiments in semiconductor nanowires with a spin-orbit coupling and proximity-induced superconductivity exhibit signatures of Majorana bound states predicted to exist in the topological phase. In this work we predict that these nanowire systems exhibit unconventional magnetoelectric effects showing a sharp crossover behavior at the topological phase transition. We find that magnetic fields with a component parallel to the spin-orbit field can give rise to currents in equilibrium. Surprisingly, also fields perpendicular to the spin-orbit field may induce currents and can be employed in adiabatic charge pumping. The perpendicular field magnetoelectric effect may be regarded as a manifestation of the anomalous Hall effect in one dimension. We discuss how the predicted phenomena could be observed in experiments and employed in probing the topological phase transition.