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

In this work we study how different atomic configurations, and electronic correlation modify the exciton dispersion in hexagonal boron nitride. We use two different approaches, ab-initio DFT plus many-body perturbation theory and tight-binding.
We found that in the case of AB-stacking electronic correlation inverts the nature of the optical gap, from indirect to direct respect to the single-particle picture.

The paper is available here: https://arxiv.org/abs/1806.06201

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