Lattice-Reconstruction-Driven Modulation in Nonlinear Optical Responses of Small-Twist-Angle Bilayer MoS2

We meticulously engineered a homogeneous bilayer structure featuring precisely defined interlayer twist angles by stacking monolayer single-crystal MoS2 in a controlled, layer-by-layer manner. Our research explores the intricate relationship between lattice reconstruction and linear and nonlinear spectroscopy by combining scanning tunneling microscopy (STM) and optical techniques. Twisted bilayer MoS2 samples with twist angles ranging from 1° to 4° were precisely prepared using the pick-up transfer method, and the resulting structures were thoroughly characterized. We revealed unexpected lattice reconstruction at twist angles of ≤ 2° and demonstrated its profound influence on the optical properties of the material.