Anisotropic interlayer exciton in black phosphorus van der Waals heterostructures

Abstract

We study theoretically the variations of interlayer exciton binding energy caused by the exciton–optical phonons coupling in van der Waals heterostructures composed of double-layer black phosphorus (BP), where both the longitudinal optical phonon modes and the surface optical phonon modes induced by the inserted h-BN layer are taken into account. We find that the strength of exciton–phonon coupling depends on the anisotropy of the effective mass of interlayer exciton, which plays a crucial rule in adjusting the binding energies of interlayer excitons. Moreover, the modulation effects of interlayer distance between two layers as well as the internal distance between BP layer and the inserted h-BN layer on the binding energies are analyzed quantitatively. These results provide theoretical insight when modulating interlayer excitons in two-dimensional van der Waals heterostructures in experiments.