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 degrees, the interlayer coupling strength is the strongest. However, when the twist angle is between 0 and 60 degrees, interlayer coupling strength becomes much weaker and reaches a minimum around 30 degrees. 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.

通过相邻两层之间的扭转角来控制范德华（vdW）同构或异构结构中的层间耦合是一种调控其电子特性的有效方法。在此，我们从实验和理论两方面系统地研究了扭转双层二硫化钨（WS₂）中层间耦合的演变。光致发光光谱和拉曼光谱表明，层间耦合对扭转角敏感。在扭转角为0度或60度的双层WS₂中，层间耦合强度最强。然而，当扭转角在0度到60度之间时，层间耦合强度变得弱得多，并在30度左右达到最小值。结合密度泛函理论计算，层间耦合的调制源于相邻两层WS₂之间的排斥导致的层间距变化。观察到自旋 - 轨道耦合（SOC）以及层间耦合诱导的高达400毫电子伏特的自旋分裂。