Twisted Schwinger effect: Geometric effects in carrier creation in semimetals
- Datum: 12.05.2021
- Uhrzeit: 15:00 - 16:00
- Vortragender: Takashi Oka
- Tokyo University
- Ort: online via Zoom
- Gastgeber: Michael Sentef
Dirac and Weyl semimetals provide a testbed for studying nonperturbative geometric effects in laser field-induced electron dynamics . There are several closely related but distinct geometric phenomena, i.e., (i) Floquet topological bands , (ii) dynamical Hall response due to the carrier motion , and (iii) pair creation . In this talk, I will mainly focus on the phenomenon (iii).
Electron and hole pairs are created when strong laser fields irradiate a Dirac or Weyl semimetal. This is known as the Schwinger effect in the high-energy physics literature and is mathematically equivalent to the Landau-Zener breakdown in semiconductor physics. It is known that geometric effects also exist in nonadiabatic processes, which was first noticed by Berry in his paper . We extend his analysis to second-order and apply it to the carrier creation in circularly polarized laser fields . Our finding predicts a nonperturbative counterpart of the circular photogalvanic effect in 3D semimetals, which might be confirmed in a ultrafast pump-probe experiments.
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