New Journal of Physics (Jan 2018)

Valley Hall transport of photon-dressed quasiparticles in two-dimensional Dirac semiconductors

  • V M Kovalev,
  • Wang-Kong Tse,
  • M V Fistul,
  • I G Savenko

DOI
https://doi.org/10.1088/1367-2630/aad5f8
Journal volume & issue
Vol. 20, no. 8
p. 083007

Abstract

Read online

We present a theory of the photovoltaic valley-dependent Hall effect in a two-dimensional (2D) Dirac semiconductor subject to an intense near-resonant electromagnetic field. Our theory captures and elucidates the influence of both the field-induced resonant interband transitions and the nonequilibrium carrier kinetics on the resulting valley Hall transport in terms of photon-dressed quasiparticles (PDQs). The non-perturbative renormalization effect of the pump field manifests itself in the dynamics of the PDQs, with a quasienergy spectrum characterized by dynamical gaps δ _η ( η is the valley index) that strongly depend on field amplitude and polarization. Nonequilibrium carrier distribution functions are determined by the pump field frequency ω as well as the ratio of intraband relaxation time τ and interband recombination time τ _rec . We obtain analytic results in three regimes, when (I) all relaxation processes are negligible, (II) τ ≪ τ _rec , and (III) τ ≫ τ _rec , and display corresponding asymptotic dependences on δ _η and ω . We then apply our theory to 2D transition-metal dichalcogenides, and find a strong enhancement of valley-dependent Hall conductivity as the pump field frequency approaches the transition energies between the pair of spin-resolved conduction and valence bands at the two valleys.

Keywords