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Virtual seminar March 6, 13H30 : Ludger Wirtz

Hexagonal Boron Nitride: New Theory Developments on a Well-Known 2D Material

Ludger Wirtz

Department of Physics and Materials Science
University of Luxembourg

https://univ-grenoble-alpes-fr.zoom.us/j/93458694522?pwd=a1FxaXpGU3ZCQVk3bkpDdjJtZlNqUT09

Next virtual seminar of the GDR : 6 March 2023, 13h30

Hexagonal Boron Nitride: New Theory Developments on a Well-Known 2D Material

Ludger Wirtz

Department of Physics and Materials Science
University of Luxembourg

Layered hexagonal Boron Nitride (hBN) is often used as a flat, clean, and well-insulating substrate for the investigation of graphene or other 2D materials. But its intrinsic optical properties - in the deep UV - are interesting by itself: the strong luminescence and its potential for UV-lasing was discovered in 2004 [1] by the group who still distributes high-quality samples of hBN to the whole 2D community. The presence of huge excitonic effects in bulk hBN was theoretically established by ab-initio calculations [2]. Soon afterwards, it was established that the binding energy in single-layer hBN is even 3 times higher [3]. Since then, the surprising complexity of the luminescence spectra of this seemingly simple material (with only 4 atoms per unit-cell for bulk hBN and 2 atoms for monolayer hBN) has attracted a lot of attention by theoretical and experimental groups likewise. A lot of the recent progress on this material has been achieved by (or in collaboration with) French research groups.

I will discuss the role of crystal symmetry in the optical spectra of hBN and explain how to understand the luminescence of different phases of BN from a theoretical/computational perspective, taking into account the strong excitonic effects and its coupling with phonons. I will give a perspective on non-adiabatic effects in the Raman spectra of bulk hBN and on the understanding of the substrate-dependence of the luminescence spectra of mono-layer hBN.

[1] K. Watanabe, T. Taniguchi and H. Kanda,
Direct-bandgap properties and evidence for ultraviolet lasing of hexagonal boron nitride single crystal,
Nature Materials 3, 404–409 (2004).
[2] B. Arnaud, S. Lebègue, P. Rabiller, and M. Alouani,
Huge Excitonic Effects in Layered Hexagonal Boron Nitride,
Phys. Rev. Lett. 96, 026402 (2006).
[3] L. Wirtz, A. Marini, and A. Rubio,
Excitons in Boron Nitride Nanotubes: Dimensionality Effects,
Phys. Rev. Lett. 96, 126104 (2006).

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Zoom connection info :

Time: Mar 6, 2023 01:30 PM Paris

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