Hinge states in a system of coupled Rashba layers

TL;DR

This paper explores how coupled Rashba layers with Zeeman fields can host various topological phases, including surface and hinge states, with analytical and numerical evidence supporting their stability.

Contribution

It introduces a model of stacked Rashba layers with Zeeman fields that reveals new topological phases, including second-order topological insulators with hinge states.

Findings

Identification of topological insulator phases with surface states

Discovery of second-order topological insulator with hinge states

Validation of phase stability against perturbations

Abstract

We consider a system of stacked tunnel-coupled two-dimensional electron- and hole-gas layers with Rashba spin-orbit interactions subjected to a staggered Zeeman field. The interplay of different intra-layer tunnel couplings results in a phase transition to a topological insulator phase in three dimensions hosting gapless surface states. The staggered Zeeman field further enriches the topological phase diagram by generating a second-order topological insulator phase hosting gapless hinge states. The emergence of the topological phases is proven analytically in the regime of small Zeeman field and confirmed by numerical simulations in the non-perturbative region of the phase diagram. The topological phases are stable against external perturbations and disorder.