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O: Fachverband Oberflächenphysik
O 53: Focus Session: Frontiers of Electronic-Structure Theory IV (joint session O/HL)
O 53.3: Talk
Wednesday, March 29, 2023, 11:15–11:30, TRE Ma
Exciton-phonon coupling in luminescence of indirect band-gap materials — Matteo Zanfrognini1,2, Fulvio Paleari1, Daniele Varsano1, and •Ludger Wirtz3 — 1Centro S3, CNR-Istituto Nanoscienze, Modena, Italy — 2Università di Modena e Reggio Emilia, Modena, Italy — 3Department of Physics and Materials Science, University of Luxembourg, Luxembourg
Layered, quasi-2D materials, such as hexagonal boron nitride (hBN) are known to display very strong excitonic effects due to the concentration of excitons in two dimensions and due to the relatively weak dielectric screening. If the band-gap of the material is indirect, the dispersion of the lowest lying exciton can have a minimum at a finite wave vector q. Upon absorption of a photon and excitation to a vertical (q=0) exciton, the system will relax to the finite-q exciton. Luminescence then entails the absorption/emission of a phonon with wave vector q. We present a computational approach for phonon-assisted luminescence in the presence of strong excitonic effects using two approaches: (i) a finite-displacement approach for the exciton-phonon coupling and (ii) a diagrammatic approach, calculating the q-dependent exciton-phonon coupling from the exciton eigenvectors and electron/hole-phonon scattering matrix elements. We show that the methodology quantitatively explains recent measurements of different stackings of BN layers. [1]
[1] A. Plaud, I. Stenger, F. Fossard, L. Sponza, L. Schué, F. Ducastelle, A. Loiseau, J. Barjon, to be published.