  The electronic properties of the twisted InSe bilayer are studied by
large-scale density functional theory. Spectral Function Unfolding reveals that
the electronic structure of the twisted system can be described in terms of a
combination of features of the bandstructures of the aligned InSe bilayer with
different stacking configurations, enabling predictions of the band gap and the
effective mass for holes. The effective mass for holes in the twisted InSe
bilayer is shown to be influenced primarily by the interlayer distance. The
intralayer and interlayer exciton binding energies are thus calculated based on
a model recently developed by Ruiz-Tijerina et al. We apply similar analysis to
the trilayer heterostructure InSe/hBN/InSe: its electronic structure is shown
to be well-described by the superposition of band structures of two InSe
monolayers with a small coupling through the hBN layer.
