A model for the direct-to-indirect band-gap transition in monolayer MoSe2 under strain

A monolayer of MoSe2 is found to be a direct band-gap semiconductor. We show, within ab-initio electronic structure calculations, that a modest biaxial tensile strain of 3% can drive it into an indirect band-gap semiconductor with the valence band maximum (VBM) shifting from K point to I" point. An analysis of the charge density reveals that while Mo-Mo interactions contribute to the VBM at 0% strain, Mo-Se interactions contribute to the highest occupied band at I" point. A scaling of the hopping interaction strengths within an appropriate tight binding model can capture the transition.