Symmetry-enforced metal-insulator transition and topological adiabatic charge pump in sliding bilayers of threefold symmetric materials

TL;DR

This paper explores how sliding bilayers of certain materials can induce a metal-insulator transition and enable a topological charge pump, combining symmetry analysis, tight-binding models, and first-principles calculations.

Contribution

It introduces a minimal model and symmetry-based analysis for sliding-induced effects, demonstrating a controllable metal-insulator transition and topological charge pump in specific bilayer materials.

Findings

Sliding induces a controllable metal-insulator transition.

Bilayer GaS exhibits the metal-insulator transition.

Bilayer ZrS₂ demonstrates a topological adiabatic charge pump.

Abstract

Sliding bilayers are systems that exploit the possibility of relatively translating two monolayers along a specific direction in real space, such that different stackings could be implemented in the process. This simple approach allows for manipulating the electronic properties of layered materials similarly as in twisted multilayers. In this work, the sliding of bilayers, composed of one type of monolayer with spatial symmetry described by space group P$\bar{3}1m$ is studied. Using a minimal tight-binding model along with symmetry analysis, we propose two effects that arise in a specific sliding direction. First, the sliding-induced control of the band gap magnitude, which produces a metal-insulator transition, is demonstrated. In addition, the potential to achieve a topological adiabatic charge pump for cyclic sliding is discussed. For each effect, we also present material implementations using first-principles calculations. Bilayer GaS is selected for the metal-insulator transition and bilayer transition metal dichalcogenide ZrS$_2$ is found to display the topological pump effect. Both realizations show good agreement with the predictions of the model.