Probing Angle-Dependent Interlayer Coupling in Twisted Bilayer WS2

Controlling the interlayer coupling in van der Waals (vdW) homo- or heterostructures by twist angle between two adjacent layers is a powerful approach to manipulate their electronic properties. Here, we systematically study the evolution of an interlayer coupling in twisted bilayer WS2 both experimentally and theoretically. Photoluminescence spectra and Raman spectra show that the interlayer coupling is sensitive to twist angle. In the bilayer WS2 with a twist angle of 0 or 60°, the interlayer coupling strength is the strongest. However, when the twist angle is between 0 and 60°, interlayer coupling strength becomes much weaker and reaches a minimum around 30°. Combined with density functional theory calculation, the modulation of interlayer coupling originates from the change of the interlayer distance due to repulsion between two adjacent WS2 layers. It is observed that spin–orbital coupling (SOC) and interlayer coupling induced spin splitting as large as 400 meV.