Journal article

Photoinduced gap closure in an excitonic insulator

  • Golež, Denis Department of Physics, University of Fribourg, Switzerland
  • Werner, Philipp Department of Physics, University of Fribourg, Switzerland
  • Eckstein, Martin Max Planck Research Department for Structural Dynamics, University of Hamburg-CFEL, Germany
Published in:
  • Physical Review B. - 2016, vol. 94, no. 3, p. 35121
English We study the dynamical phase transition out of an excitonic insulator phase after photoexcitation using a time-dependent extension of the self-consistent GW method. We connect the evolution of the photoemission spectra to the dynamics of the excitonic order parameter and identify two dynamical phase transition points marked by a slowdown in the relaxation: one critical point is connected with the trapping in a nonthermal state with reduced exciton density and the second corresponds to the thermal phase transition. The transfer of kinetic energy from the photoexcited carriers to the exciton condensate is shown to be the main mechanism for the gap melting. We analyze the low energy dynamics of screening, which strongly depends on the presence of the excitonic gap, and argue that it is difficult to interpret the static component of the screened interaction as the effective interaction of some low energy model. Instead we propose a phenomenological measure for the effective interaction which indicates that screening has minor effects on the low energy dynamics.
Faculté des sciences et de médecine
Département de Physique
  • English
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