Influence of the Twist Angle and Spin–Orbit Coupling on the Interlayer Coupling and Optoelectronic Properties of MoS2/WS2 Superlattice Heterostructures

Abstract

Twisted 2D bilayer transition metal dichalcogenides (TMDs) heterostructures exhibit rich physical properties due to the interaction of interlayer coupling and moiré superlattice effects. However, the influence of interlayer coupling changes induced by the twist angle on various TMDs properties still requires further exploration. To systematically investigate how the twist angle influences the structural, electronic and optical properties of TMDs, density functional theory (DFT) is used to examine $\sqrt{7}$ MoS₂/WS₂ superlattice heterostructures. Compared with that of the 2H stack, the interlayer coupling effect is weakened in the 21.79° and particularly 38.21° stacked heterostructures. A larger twist angle promotes an indirect-to-direct bandgap transition trend. Additionally, the twist angle can cause interlayer charge redistribution, which varies with the moiré pattern. Moreover, spin‒orbit coupling (SOC) causes a redshift by reducing the bandgap in the absorption spectra, and the twist angle suppresses interlayer direct transitions in the 𝜥 valley and alters the Raman and infrared spectra, with low-frequency Raman modes providing a powerful tool for characterizing changes in interlayer coupling. These findings highlight the critical role of the twist angle in tuning the properties of TMDs heterostructures, with promising implications for optoelectronic and valleytronic applications.