How Can We Engineer Electronic Transitions Through Twisting and Stacking in TMDC Bilayers and Heterostructures? A First-Principles Approach

TL;DR

This study uses first-principles calculations to explore how twisting and stacking in TMDC bilayers and heterostructures can be engineered to modify electronic properties, revealing critical angles and configurations for desired band gap behaviors.

Contribution

It provides a comprehensive first-principles analysis of 30 TMDC combinations, demonstrating how stacking and twist angles influence stability and electronic properties, including direct-indirect band gap transitions.

Findings

Certain twist angles induce symmetric Moiré patterns with tunable band gaps.

Heterostructures like MoTe$_2$/WSe$_2$ maintain direct band gaps at specific shifts.

MoS$_2$ can switch between semiconductor and metallic states depending on stacking.

Abstract

Layered two-dimensional (2D) materials exhibit unique properties, expanding opportunities in material design. We investigate MX$_2$ transition metal dichalcogenides (TMDCs) (M = Mo, W; X = S, Se, Te) in homo- and heterobilayers with different stacking and twist angles. Twisted bilayers introduce Moir\'e patterns, significantly altering electronic properties. Using first-principles Density Functional Theory (DFT) with range-separated hybrid functionals, we examine 30 MX$_2$ combinations, revealing how stacking and composition influence stability and band gap energy (E$_g$). Notably, the MoTe$_2$/WSe$_2$ heterostructure with a 60\textdegree~shift maintains a direct band gap, highlighting its potential for applications. Homobilayers under low-strain conditions exhibit diverse stacking-dependent electronic behaviors, where MoS$_2$, WS$_2$, and WSe$_2$ transition between direct and indirect band gaps at specific twist angles. MoS$_2$ can even switch between semiconductor and metallic states. Critical twist angles (17.9\textdegree, 42.1\textdegree, 77.9\textdegree, and 102.1\textdegree) in twisted WS$_2$ and WSe$_2$ bilayers yield symmetric Moir\'e patterns with tunable band gaps. Our findings emphasize that controlling heterostructures and twist angles is a powerful strategy for engineering electronic properties, offering a pathway for next-generation materials.