Twist angle control of excited states in transition metal dichalcogenide bilayers*

A new type of superlattice, known as the moiré superlattice, form when two monolayers of van der Waals materials are vertically stacked. A periodic energy modulation, as well as distinct optical selection rules, gives rise to rich optical properties. In this talk, I will discuss how the twist angle controls the exciton resonances, lifetimes, diffusion in transition metal dichalcogenide heterobilayers. It is possible to control the twist angle with a higher degree of accuracy in homobilayers, we show that lattice reconstruction occurs over a rather large range, as manifested in Raman spectra.