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SUMMARY:Non-linear response of two dimensional crystals and layered materi
 als - Dr Claudio Attaccalite\, CNRS
DTSTART:20190214T141500Z
DTEND:20190214T151500Z
UID:TALK109657@talks.cam.ac.uk
CONTACT:Bartomeu Monserrat
DESCRIPTION:Starting since 2013 we have been developing a real-time approa
 ch to study nonlinear optical properties in periodic systems [1]. In this 
 approach the non-linear response is obtained from the time evolution of an
  effective Schroedinger equation. In this talk I will introduce non-linear
  response in solids and show how it can be calculated by means of Modern T
 heory of Polarization plus a real-time dynamics.\nThen I will present diff
 erent applications to the second harmonic generation (SHG) in hBN and MoS2
  [2]\, where the inclusion of excitonic effect is crucial to reproduce the
  experimental results.  A final example will be the two-photon absorption 
 (TPA) in bulk and single layer hexagonal boron nitride (hBN) [3]. The TPA 
 obeys to different selection rules from those governing linear optics and 
 therefore provides complementary information on the electronic excitations
  of hBN. Combining the results from the simulations with a symmetry analys
 is we show that two-photon absorption is able to probe lowest dark degener
 ate states of bulk hBN.  \n\n[1] Nonlinear optics from an ab initio approa
 ch by means of the dynamical Berry phase: Application to second-and third-
 harmonic generation in semiconductors \nC Attaccalite\, M Grüning\, Physi
 cal Review B 88 (23)\, 235113 (2013)\n\n[2] Second harmonic generation in 
 h-BN and MoS2 monolayers: Role of electron-hole interaction\nM Grüning\, 
 C Attaccalite\, Physical Review B 89 (8)\, 081102 (2014)\n\n[3] Two-photon
  absorption in two-dimensional materials: The case of hexagonal boron nitr
 ide\nC Attaccalite\, M Grüning\, H Amara\, S Latil\, F Ducastelle\nPhysic
 al Review B 98\, 165126 (2018)\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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