Chemically-tailored semiconductor moiré superlattices

The nanoscale periodic potential generated from moiré superlattices provides a new knob to tune and study the flat band effect and correlated physics. To date, moiré superlattices have been obtained using various two-dimensional (2D) materials, such as graphene, hexagonal boron nitride (hBN), transition metal dichalcogenides (TMDCs), and so on. In the 2D materials family, Janus monolayers of TMDCs have two different chalcogen atoms above and below the central metal atom. This asymmetric structure induced an out-of-plane electric field which provides an additional degree of freedom in moiré superlattices. Novel features in Janus materials were predicted by recent theoretical studies, such as: large Rashba spin–orbit coupling [1] , piezoelectricity [2] , and long-lived charge-transfer excitons [3] . Furthermore, recent calculations showed that excitons in Janus heterobilayer moiré superlattices are possible to realize high-temperature Bose–Einstein condensation state [3] .