Direct and indirect excitons in boron nitride polymorphs: a story of atomic configuration and electronic correlation

Abstract

We compute and discuss the electronic band structure and excitonic dispersion of hexagonal boron nitride (hBN) in the single layer configuration and in three bulk polymorphs (usual AA' stacking, Bernal AB, and rhombohedral ABC). We focus on the changes in the electronic band structure and the exciton dispersion induced by the atomic configuration and the electron-hole interaction. Calculations are carried out on the level of \textit{ab initio} many-body perturbation theory (GW and Bethe Salpeter equation) and by means of an appropriate tight-binding model. We confirm the change from direct to indirect electronic gap when going from single layer to bulk systems and we give a detailed account of its origin by comparing the effect of different stacking sequences. We emphasize that the inclusion of the electron-hole interaction is crucial for the correct description of the momentum-dependent dispersion of the excitations. It flattens the exciton dispersion with respect to the one obtained from the dispersion of excitations in the independent-particle picture. In the AB stacking this effect is particularly important as the lowest-lying exciton is predicted to be direct despite the indirect electronic band gap.

arXiv comment19 pages, 14 figures, 7 appendixes

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• Phonon-assisted luminescence in defect centers from many-body perturbation theory
• Giant exciton-phonon coupling and zero-point renormalization in hexagonal monolayer boron nitride
• Structural, electronic, and optical properties of periodic graphene/h-BN van der Waals heterostructures
• Cathodoluminescence spectroscopy of monolayer hexagonal boron nitride
• Excitons in twisted AA' hexagonal boron nitride bilayers
• Optical spectra of 2D monolayers from time-dependent density functional theory
• Quasiparticle and Excitonic Structures of Few-layer and Bulk GaSe: Interlayer Coupling, Self-energy, and Electron-hole Interaction
• The exciton-polariton properties of hexagonal BN based microcavity and their potential applications in BEC and superconductivity
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• Solitons in binary compounds with stacked two-dimensional honeycomb lattices