Floquet Valley-Polarized Quantum Anomalous Hall State in Nonmagnetic Heterobilayers

TL;DR

This paper proposes a method to realize a valley-polarized quantum anomalous Hall state in nonmagnetic heterobilayers using light, enabling optically switchable topological states for spintronics and valleytronics.

Contribution

It introduces a novel mechanism to achieve Floquet VQAH states in nonmagnetic systems via light irradiation, expanding the scope beyond magnetic materials.

Findings

Circularly polarized light induces VQAH state from VQSH in heterobilayers.

First-principles calculations confirm the optical control of topological states.

The approach enables optically switchable topological spin-valley filtering.

Abstract

The valley-polarized quantum anomalous Hall (VQAH) state, which forwards a strategy for combining valleytronics and spintronics with nontrivial topology, attracts intensive interest in condensed-matter physics. So far, the explored VQAH states have still been limited to magnetic systems. Here, using the low-energy effective model and Floquet theorem, we propose a different mechanism to realize the Floquet VQAH state in nonmagnetic heterobilayers under light irradiation. We then realize this proposal via first-principles calculations in transition metal dichalcogenide heterobilayers, which initially possess the time-reversal invariant valley quantum spin Hall (VQSH) state. By irradiating circularly polarized light, the time-reversal invariant VQSH state can evolve into the VQAH state, behaving as an optically switchable topological spin-valley filter. These findings not only offer a rational scheme to realize the VQAH state without magnetic orders, but also pave a fascinating path for designing topological spintronic and valleytronic devices.