Optical measurements of twisted bilayer transition metal dichalcogenides

Two-dimensional Van der Waals material has become an exciting field. One of the reason is that
this system provides multiple degrees of freedom, including stacking order, interlayer spacing
and interlayer twist angle, to engineer the material band structure. Manipulation of these degrees of
freedom has led to observation of several emergent phenomena, including the fractal quantum
Hall effect, tunable Mott insulators, and unconventional superconductivity. In particular,
interlayer interaction in van der Waals heterostructures at different twist angle could induce
many exotic phenomena. How the interlayer interaction affects the electronic structure of a
material is a fundamental question. In this study, we report optical measurements of twisted bilayer
transition-metal dichalcogenides (TMDs) and demonstrate how its band structure vary with twist
angle. These results broaden the application range of van der Waals heterostructure for future
optoelectronic devices.