Hinge States of Second-Order Topological Insulators as a Mach-Zehnder Interferometer

TL;DR

This paper proposes using hinge states in second-order topological insulators as a Mach-Zehnder interferometer, demonstrating how chiral hinge modes can be manipulated for quantum interference applications.

Contribution

It introduces a novel approach to realize a Mach-Zehnder interferometer using hinge states in second-order topological insulators, supported by concrete lattice model calculations.

Findings

Hinge states can act as beam splitters for chiral modes.

A lattice model demonstrates the feasibility of the proposed interferometer.

Chiral hinge modes enable quantum interference in topological insulators.

Abstract

Three-dimensional higher-order topological insulators can have topologically protected chiral modes propagating on their hinges. Hinges with two co-propagating chiral modes can serve as a "beam splitter" between hinges with only a single chiral mode. Here we show how such a crystal, with Ohmic contacts attached to its hinges, can be used to realize a Mach-Zehnder interferometer. We present concrete calculations for a lattice model of a first-order topological insulator in a magnetic field, which, for a suitable choice of parameters, is an extrinsic second-order topological insulator with the required configuration of chiral hinge modes.