Twisted Schwinger effect: Geometric effects in carrier creation in semimetals
- Date: May 12, 2021
- Time: 15:00 - 16:00
- Speaker: Takashi Oka
- Tokyo University
- Location: online via Zoom
- Host: 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.
 McIver et. al., Nature Physics 16 , 38 (2020).
 S. A. Sato, et al., Phys. Rev. B 99, 214302 (2019).
 TO, Aoki PRB79, 081406 (2009).
 S. Takayoshi, J. Wu, TO, arXiv:2005.01755.
 M. V. Berry, Proc. Roy. Soc. Lond. A 430, 405 (1990).