Intrinsic Time-reversal-invariant Topological Superconductivity in Thin Films of Iron-based Superconductors

TL;DR

This paper proposes that thin films of iron-based superconductors can host intrinsic time-reversal-invariant helical topological superconductivity, with electric fields and magnetic fields enabling control and realization of Majorana modes.

Contribution

It introduces a new high-temperature platform for helical topological superconductivity in FeSC thin films, utilizing Dirac surface states and bulk pairing, with electric and magnetic field control.

Findings

Electric field acts as a topological switch for Majorana modes.

In-plane magnetic field induces higher-order TSC with corner Majorana zero modes.

FeSC thin films can host intrinsic helical topological superconductivity.

Abstract

We establish quasi-two-dimensional thin films of iron-based superconductors (FeSCs) as a new high-temperature platform for hosting intrinsic time-reversal-invariant helical topological superconductivity (TSC). Based on the combination of Dirac surface state and bulk extended $s$-wave pairing, our theory should be directly applicable to a large class of experimentally established FeSCs, opening a new TSC paradigm. In particular, an applied electric field serves as a "topological switch" for helical Majorana edge modes in FeSC thin films, allowing for an experimentally feasible design of gate-controlled helical Majorana circuits. Applying an in-plane magnetic field drives the helical TSC phase into a higher-order TSC carrying corner-localized Majorana zero modes. Our proposal should enable the experimental realization of helical Majorana fermions.