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

Lorenzo Sponza (1) , Hakim Amara (1) , Claudio Attaccalite (2, 3) , Sylvain Latil (4) , Thomas Galvani (5) , Fulvio Paleari (5) , Ludger Wirtz (6) , François Ducastelle (1)

1 LEM - ONERA - CNRS - Laboratoire d'étude des microstructures [Châtillon]
2 CINaM - Centre Interdisciplinaire de Nanoscience de Marseille
3 CNRS - Centre National de la Recherche Scientifique
4 GMT - Groupe Modélisation et Théorie
5 Physics and Materials Science Research Unit, University of Luxembourg
6 Physics and Materials Science Research Unit

We present a detailed discussion of 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 at the level of ab initio many-body perturbation theory (GW and Bethe Salpeter equation) and of a purposely developed 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. As a result the electron-hole dispersion is flatter than the one obtained from the band structure. 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.

Keywords: Boron nitride; Hexagonal boron nitride; Electronic band structure calculation; Bulk polymorphs; Atomic configuration; Electronic correlation calculations

Domains: Physics [physics]; Condensed Matter [cond-mat]; Materials Science [cond-mat.mtrl-sci]; Physics [physics]; Condensed Matter [cond-mat]

Lorenzo Sponza, Hakim Amara, Claudio Attaccalite, Sylvain Latil, Thomas Galvani, et al.. Direct and indirect excitons in boron nitride polymorphs: a story of atomic configuration and electronic correlation. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2018, 98 (12), pp.125206. ⟨10.1103/PhysRevB.98.125206⟩. ⟨hal-01820825⟩