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SUMMARY:Phonon assisted luminescence in hexagonal Boron Nitride - Dr Elena
  Cannuccia\, University of Rome &quot\;Tor Vergata&quot\;
DTSTART:20190117T141500Z
DTEND:20190117T151500Z
UID:TALK109651@talks.cam.ac.uk
CONTACT:Bartomeu Monserrat
DESCRIPTION:Hexagonal Boron Nitride (hBN)\, as graphite\, is a lamellar co
 mpound\, both have the same honeycomb structure inside a monolayer. They a
 lso share many physical properties and they can be exfoliated in monolayer
 s for Van der Waals heterostructures. However a difference does exist\, gr
 aphite is a gapless compound while hBN is a wide band gap material. In par
 ticular first principles calculations agree upon the existence of an indir
 ect quasiparticle band gap : the conduction band minimum sits at the M poi
 nt while the valence band maximum is around the K point of the Brillouin z
 one.\n\nOn the experimental side the nature of the electronic band structu
 re of hBN has animated a long-standing debate. Pioneering works of Watanab
 e et al. [1] have revealed the high UV radiative efficiency of hBN at room
  temperature. He first came to the conclusion that hBN was driven by direc
 t excitonic recombination. Recently Cassabois et al. [2] instead explained
  the luminescence lines to phonon-assisted recombination from an indirect 
 exciton.\n\nAiming to describe phonon-assisted luminescence a theoretical 
 formulation that combines electron-hole interactions and electron-phonon c
 oupling is needed. In recent years the method of finite differences [3] tu
 rned out to be a powerful tool to treat the electron-phonon coupling in a 
 perturbative way. So we combine Green’s function theory with finite diff
 erence electron-phonon coupling to get an accurate description of the phon
 on assisted luminescence spectrum of hBN.\n\n[1] Watanabe et al. Nature Ma
 terials 3\, 404 (2004)\n[2] Cassabois et al. Nature Photonics\, 10\, 262 (
 2016)\n[3] B. Monserrat\, Journal of Physics: Condensed Matter 30\, 083001
  (2018)
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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