When two atomically thin van der Waals (vdW) layers are vertically stacked together, the atomic alignment between the layers exhibits periodical variations, leading to a new type of in-plane superlattices known as the moiré superlattices. The twist angle controls the size of the moiré supercells and acts as a unique knob to control the material properties. In this talk, I will discuss how new excited states (excitons and phonons) emerge in highly tunable semiconductor moiré superlattices and the challenges one faces when trying to interpret optical measurements on these systems.  

Please contact phweb@ust.hk should you have questions about the talk.