Majorana Kramers pairs in higher-order topological insulators

TL;DR

This paper proposes a magnetic-field-free, interaction-stabilized method to realize Majorana Kramers pairs in higher-order topological insulators by inducing topological superconductivity at their hinges through proximity effects.

Contribution

It introduces a novel, tune-free scheme for creating Majorana Kramers pairs in HOTIs using proximity-induced superconductivity without magnetic fields or local gates.

Findings

Majorana Kramers pairs can be realized in HOTIs via hinge proximity to s-wave superconductors.

Moderate electron-electron interactions stabilize the topological superconducting phase.

The scheme avoids magnetic fields and requires weaker interactions than nanowire approaches.

Abstract

We propose a tune-free scheme to realize Kramers pairs of Majorana bound states in recently discovered higher-order topological insulators (HOTIs). We show that, by bringing two hinges of a HOTI into the proximity of an $s$-wave superconductor, the competition between local and crossed-Andreev pairing leads to the formation of Majorana Kramers pairs, when the latter pairing dominates over the former. We demonstrate that such a topological superconductivity is stabilized by moderate electron-electron interactions. The proposed setup avoids the application of a magnetic field or local voltage gates, and requires weaker interactions compared with nonhelical nanowires.