Commensurate structures in twisted transition metal dichalcogenide heterobilayers

TL;DR

This paper investigates twisted transition metal dichalcogenide bilayers by analyzing their commensurate structures using density functional theory, revealing how variations in stacking influence electronic and optical properties.

Contribution

It introduces a method to study large moiré patterns by focusing on constituent commensurate structures, providing detailed band structure analysis for different configurations.

Findings

Band structure varies with stacking geometry and composition.

Differences in interlayer hybridization affect electronic properties.

Strain influences moiré pattern electronic behavior.

Abstract

A major theoretical challenge of studying twisted transition metal dichalcogenide (TMD) bilayers is that the unit cell of such structures is very large and therefore difficult to address using first-principles methods. However, twisted TMD bilayers form moir\'e patterns, which consist of regions of commensurate stacking, either smoothly interpolated into one another or separated by sharp domain walls. In this paper, we study twisted TMD bilayers by studying the properties of the constituent commensurate structures. Using density functional theory (DFT), we compute band structures for commensurately-stacked MoS$_2$/WS$_2$ and MoSe$_2$/WSe$_2$ bilayers in both $0^\circ$ and $60^\circ$ orientations, and we highlight variations in band structures across different commensurate geometries. These band structure variations arise from diverse factors such as metal atom asymmetry between layers (Mo vs. W), differences in interlayer hybridization, and Brillouin zone alignment. We comment on the consequences of such band structure differences for optical experiments and on the effects of strain on moir\'e pattern electronic structure.