How Can We Engineer Electronic Transitions Through Twisting and Stacking in TMDC Bilayers and Heterostructures? A First-Principles Approach (2405.06096v2)

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.