Electronic and Optical Properties of Pristine and Vertical and Lateral Heterostructures of Janus MoSSe and WSSe.

On the basis of electron-electron self-energy corrections, quasiparticle band structures of Janus MoSSe and WSSe are identified, and the excitonic effects are demonstrated to play a dominate role in the optical response. Combining together MoSSe and WSSe monolayers to form vertical heterostructures (VHTs) and lateral heterostructures (LHTs) rarely leads to a simple arithmetic sum of their properties, giving rise to novel and unexpected behaviors. In particular, Rashba polarization can be enhanced in VHTs due to improved out-of-plane electric polarity. In the case of LHTs, photoresponse and absorption coefficients show optical activity in a wide visible light range. It is of interest that both VHTs and LHTs reveal type-II band alignment, enabling the separation of excitons. Besides, grain boundaries (GBs) of large angle (60°) in Janus MoSSe due to chalcogen effects behave as one-dimensional (1D) metallic quantum wires, suggesting the possible formation of 1D electron or hole gas in such electronic heterostructures.