Excitonic Effects in Hexagonal Boron Nitride Multilayer Systems
ORAL
Abstract
Hexagonal boron nitride (hBN) is a layered material and an insulator displaying strong excitonic effects.
We investigate theoretically the effects of layer stacking on the optical properties of few-layer hBN systems.
Using both ab initio simulations and a tight-binding model for an effective Hamiltonian describing the excitons, we show that the fine structure of the optical absorption spectra is characterized by the the splitting between low-lying surface excitons, that are mostly localized on the outer layers, and inner, bulk-like excitons.
Moreover, in the case of single-layer hBN, we study the correction to the first excitonic peak due to exciton-phonon interaction.
We compare a single-phonon, dynamical method [Marini, PRL 101, 2008] based on the calculation of the electron-phonon self-energy with the static, multi-phonon Williams-Lax theory [Zacharias et al, PRL 115, 2015] applied to the Bethe-Salpeter equation.
We find a strong redshift of the exciton peak (around 0.5 eV), but a relatively small broadening.
In the case of bulk hBN, we perform finite-differences simulations on static atomic displacements to investigate the cross section of phonon-assisted indirect absorption and excitation of finite-q excitons.
We investigate theoretically the effects of layer stacking on the optical properties of few-layer hBN systems.
Using both ab initio simulations and a tight-binding model for an effective Hamiltonian describing the excitons, we show that the fine structure of the optical absorption spectra is characterized by the the splitting between low-lying surface excitons, that are mostly localized on the outer layers, and inner, bulk-like excitons.
Moreover, in the case of single-layer hBN, we study the correction to the first excitonic peak due to exciton-phonon interaction.
We compare a single-phonon, dynamical method [Marini, PRL 101, 2008] based on the calculation of the electron-phonon self-energy with the static, multi-phonon Williams-Lax theory [Zacharias et al, PRL 115, 2015] applied to the Bethe-Salpeter equation.
We find a strong redshift of the exciton peak (around 0.5 eV), but a relatively small broadening.
In the case of bulk hBN, we perform finite-differences simulations on static atomic displacements to investigate the cross section of phonon-assisted indirect absorption and excitation of finite-q excitons.
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Presenters
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Fulvio Paleari
University of Luxembourg Limpertsberg
Authors
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Fulvio Paleari
University of Luxembourg Limpertsberg
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Thomas Galvani
University of Luxembourg Limpertsberg
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Marios Zacharias
University of Oxford
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Alejandro Molina-Sanchez
Materials Science Institute, University of Valencia, Institute of Materials Science, University of Valencia, Institute of Materials Science (ICMUV), University of Valencia, University of Valencia
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Hakim Amara
ONERA-CNRS
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François Ducastelle
ONERA-CNRS
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Feliciano Giustino
University of Oxford
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Ludger Wirtz
Physics and Materials Science Research Unit, University of Luxembourg, University of Luxembourg Limpertsberg, University of Luxembourg