Theory and Experimental Investigation of the Quantum Valley Hall Effect

TL;DR

This paper presents a new method to precisely relate the quantum valley Hall effect to quantum spin-Hall insulators, providing quantitative insights into its robustness and experimental validation using a novel spinner-based platform.

Contribution

It introduces a technique to connect QVHE systems with quantum spin-Hall insulators without extreme limits, enabling precise analysis of QVHE's properties and robustness.

Findings

Established a quantitative relationship between QVHE and quantum spin-Hall insulators.

Demonstrated the robustness of QVHE against disorder.

Provided experimental evidence using magnetically coupled spinners.

Abstract

The quantum valley Hall effect (QVHE) has been observed in a variety of experimental setups, both quantum and classical. While extremely promising for applications, one should be reminded that QVHE is not an exact topological phenomenon and that, so far, it has been fully understood only qualitatively in certain extreme limits. Here we present a technique to relate QVHE systems with exact quantum spin-Hall insulators that accept real-space representations, without taking any extreme limit. Since the bulk-boundary correspondence is well understood for the latter, we are able to formulate precise quantitative statements about the QVHE regime and its robustness against disorder. We further investigate the effect using a novel experimental platform based on magnetically coupled spinners. Visual renderings, quantitative data and various tests of the domain-wall modes are supplied, hence giving an unprecedented insight into the effect.