Majorana zero modes induced by superconducting phase bias

TL;DR

This paper reviews proposals for inducing Majorana zero modes through superconducting phase control, offering potential improvements over magnetic methods and advancing understanding of topological superconductivity.

Contribution

It introduces phase bias techniques as a novel approach to realize Majorana zero modes, reducing reliance on magnetic fields and highlighting their practical advantages.

Findings

Phase control can induce Majorana zero modes without magnetic fields

Superconducting phase bias reduces unwanted side effects

Enhances understanding of topological superconducting states

Abstract

Majorana zero modes in condensed matter systems have been the subject of much interest in recent years. Their non-Abelian exchange statistics, making them a unique state of matter, and their potential applications in topological quantum computation, earned them attention from both theorists and experimentalists. It is generally understood that in order to form Majorana zero modes in quasi-one-dimensional topological insulators, time-reversal symmetry must be broken. The straightforward mechanisms for doing so -- applying magnetic fields or coupling to ferromagnets -- turned out to have many unwanted side effects, such as degradation of superconductivity and the formation of sub-gap states, which is part of the reason Majorana zero modes have been eluding direct experimental detection for a long time. Here we review several proposal that rely on controlling the phase of the superconducting order parameter, either as the sole mechanism for time-reversal-symmetry breaking, or as an additional handy knob used to reduce the applied magnetic field. These proposals hold practical promise to improve Majorana formation, and they shed light on the physics underlying the formation of the topological superconducting state.