Three-phase Majorana zero modes at tiny magnetic fields

TL;DR

This paper proposes a novel method to realize Majorana zero modes using phase-biased superconductors and tiny magnetic fields, avoiding the detrimental effects of magnetic fields on superconductors.

Contribution

It introduces a new scheme for Majorana realization relying solely on phase biasing and supercurrents, eliminating the need for strong magnetic fields.

Findings

Majorana modes can be achieved with tiny magnetic fields in phase-biased superconducting loops.

The scheme combines superconducting phase winding and spin-orbit effects to create topological states.

Simulations confirm the feasibility of realizing Majoranas with conventional materials.

Abstract

Proposals for realizing Majorana fermions in condensed matter systems typically rely on magnetic fields, which degrade the proximitizing superconductor and plague the Majoranas' detection. We propose an alternative scheme to realize Majoranas based only on phase-biased superconductors. The phases (at least three of them) can be biased by a tiny magnetic field threading macroscopic superconducting loops, focusing and enhancing the effect of the magnetic field onto the junction, or by supercurrents. We show how a combination of the superconducting phase winding and the spin-orbit phase induced in closed loops (Aharonov-Casher effect) facilitates a topological superconducting state with Majorana end states. We demontrate this scheme by an analytically tractable model as well as simulations of realistic setups comprising only conventional materials.