How Can We Engineer Electronic Transitions Through Twisting and Stacking in TMDC Bilayers and Heterostructures? A First-Principles Approach
Abstract
Layered two-dimensional (2D) materials exhibit unique properties, expanding opportunities in material design. We investigate MX2 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 MX2 combinations, revealing how stacking and composition influence stability and band gap energy (Eg). Notably, the MoTe2/WSe2 heterostructure with a 60~shift maintains a direct band gap, highlighting its potential for applications. Homobilayers under low-strain conditions exhibit diverse stacking-dependent electronic behaviors, where MoS2, WS2, and WSe2 transition between direct and indirect band gaps at specific twist angles. MoS2 can even switch between semiconductor and metallic states. Critical twist angles (17.9, 42.1, 77.9, and 102.1) in twisted WS2 and WSe2 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.
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