Electrical manipulation of Majorana fermions in an interdigitated superconductor-ferromagnet device

TL;DR

This paper proposes a 2D electron gas device with interdigitated superconductor-ferromagnet structures to realize and detect Majorana fermions through electrical control and characteristic interference patterns.

Contribution

It introduces a novel interdigitated device design that supports a topological phase with Majorana fermions, enabling easier experimental realization and detection.

Findings

Topological phase supported when finger spacing is less than half the Fermi wavelength.

Robust Majorana-supporting phase persists even when finger spacing exceeds half the Fermi wavelength.

Predicted anomalous Fraunhofer pattern as a signature of chiral Majorana edge states.

Abstract

We show that a topological phase supporting Majorana fermions can form in a 2D electron gas (2DEG) adjacent to an interdigitated superconductor-ferromagnet structure. An advantage of this setup is that the 2DEG can induce the required Zeeman splitting and superconductivity from a single interface, allowing one to utilize a wide class of 2DEGs including the surface states of bulk InAs. We demonstrate that the interdigitated device supports a robust topological phase when the finger spacing lambda is smaller than half of the Fermi wavelength lambda_F. In this regime, the electrons effectively see a "smeared" Zeeman splitting and pairing field despite the interdigitation. The topological phase survives even in the opposite limit lambda>lambda_F/2, though with a reduced bulk gap. We describe how to electrically generate a vortex in this setup to trap a Majorana mode, and predict an anomalous Fraunhofer pattern that provides a sharp signature of chiral Majorana edge states.