Ferroelectric topological superconductor

TL;DR

This paper introduces the concept of ferroelectric topological superconductors (FE TSCs), which are electrically tunable quantum materials hosting Majorana modes, with potential applications in fault-tolerant quantum computing.

Contribution

It proposes the FE TSC concept, demonstrating electrical tunability of domain-wall Majorana modes and identifying $ ext{In}_2 ext{Se}_3$ as a promising candidate through first-principles calculations.

Findings

FE polarization controls the $ ext{pi}$-phase shift in pairing gap.

Reversing FE polarization switches Majorana modes.

$ ext{In}_2 ext{Se}_3$ is a promising FE TSC candidate.

Abstract

Two-dimensional topological superconductor (TSC) represents an exotic quantum material with quasiparticle excitation manifesting in dispersive Majorana mode (DMM) at the boundaries. A domain-wall DMM can arise at the boundary between two TSC domains with opposite Chern numbers or with a $\pi$-phase shift in their pairing gap, which can only be tuned by magnetic field. Here we propose the concept of ferroelectric (FE) TSC, which not only enriches the domain-wall DMMs but also significantly makes them electrically tunable. The $\pi$-phase shift of the pairing gap is shown to be attained between two TSC domains of opposite FE polarization, and switchable by reversing FE polarizations. In combination with ferromagnetic (FM) polarization, the domain wall can host helical, doubled chiral, and fused DMMs, which can be transferred into each other by changing the direction of electrical and/or magnetic field. Furthermore, based on first-principles calculations, we demonstrate $\alpha$-In$_2$Se$_3$ to be a promising FE TSC candidate in proximity with a FM layer and a superconductor substrate. We envision that FE TSC will significantly ease the manipulation of DMM by electrical field to realize fault-tolerant quantum computation.