Tight-Binding Model

In this chapter, we present a description of the electronic and optical properties of mono- and few-layer InSe in the context of a tight-binding model. We find a marked change in the band gap on going from the bulk (band gap $$\sim $$ 1.3 eV) to the monolayer (band gap $$\sim $$ 2.8 eV) case, in agreement with experiment. We find that the principal interband optical transition is of a dominantly out-of-plane polarised character, with the oscillator strength increasing for thicker crystals, while the next-lowest energy transition couples strongly to in-plane polarised light, with an oscillator strength which is largely independent of the number of layers.