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Photoinduced enhancement of excitonic order

  • Murakami, Yuta Department of Physics, University of Fribourg, Switzerland
  • Golež, Denis Department of Physics, University of Fribourg, Switzerland
  • Eckstein, Martin Department of Physics, University of Erlangen-Nürnberg, Germany
  • Werner, Philipp Department of Physics, University of Fribourg, Switzerland
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  • Physical Review Letters. - 2017, vol. 119, no. 24, p. 247601
English We study the dynamics of excitonic insulators coupled to phonons using the time- dependent mean-field theory. Without phonon couplings, the linear response is given by the damped amplitude oscillations of the order parameter with a frequency equal to the minimum band gap. A phonon coupling to the interband transfer integral induces two types of long-lived collective oscillations of the amplitude, one originating from the phonon dynamics and the other from the phase mode, which becomes massive. We show that, even for small phonon coupling, a photoinduced enhancement of the exciton condensation and the gap can be realized. Using the Anderson pseudospin picture, we argue that the origin of the enhancement is a cooperative effect of the massive phase mode and the Hartree shift induced by the photoexcitation. We also discuss how the enhancement of the order and the collective modes can be observed with time-resolved photoemission spectroscopy.
Faculté des sciences et de médecine
Département de Physique
  • English
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