Two-particle Berry phase mechanism for Dirac and Majorana Kramers pairs of corner modes

TL;DR

This paper introduces a new two-particle Berry phase mechanism that enables the realization of Dirac and Majorana Kramers pairs at the corners of second-order topological insulators and superconductors with time-reversal symmetry, using edge state pseudospin textures and external fields.

Contribution

It proposes a novel two-particle Berry phase mechanism for corner modes in topological materials, enabling Majorana Kramers pairs without complex superconducting junctions.

Findings

Predicts Majorana Kramers pairs in a simple TI-superconductor setup

Identifies Au/GaAs(111) as a candidate material for experimental realization

Demonstrates a new geometric phase mechanism for topological corner modes

Abstract

We uncover a novel two-particle Berry phase mechanism to realize exotic corner modes in second-order topological insulators (TIs) and topological superconductors (TSCs) with time-reversal symmetry. We show that the nontrivial pseudospin textures of edge states in two different types of two-dimensional TIs give rise to the novel two-particle geometric phases in the particle-hole and particle-particle channels, respectively, for which the edge mass domain walls or intrinsic $\pi$-junctions emerge across corners when an external magnetic field or $s$-wave superconductivity is considered, hosting Dirac or Majorana corner modes. Remarkably, with this mechanism we predict the Majorana Kramers pair of corner modes by directly coupling the edge of a type-II time-reversal invariant TI to a uniform $s$-wave SC, in sharp contrast to the previous proposals which rely on unconventional SC pairing or complex setting for fine-tuned SC $\pi$-junction. We find Au/GaAs(111) to be a realistic material candidate for realizing such Majorana Kramers pair of corner modes.