Emergence of valley selectivity in monolayer tin(ii) sulphide.

The emergence of valley selectivity in tin(ii) sulphide is explained with the use of density functional theory and the momentum operator matrix elements for the optical transitions. After application of electric stress, the polarization efficiency was found to decrease in the zigzag direction. Wannier functions are further used to derive an effective Tight Binding (TB) model. The velocity matrix elements of the Wannier functions reveal further details about how the p orbitals of Sn and S contribute to optical transitions. Using the TB model in the Wannier basis in a nanoribbon configuration, the bandgap shows an overall decrease as the width of the nanoribbon increases for both zigzag and armchair directions of the structure up to ≈42 Å further presenting opportunities for Optoelectronic applications.