Valley Hall Transport of Photon-Dressed Quasiparticles in 2D Dirac Semiconductors

TL;DR

This paper develops a theoretical framework for understanding how intense electromagnetic fields induce valley-dependent Hall effects in 2D Dirac semiconductors through photon-dressed quasiparticles, revealing enhanced valley Hall conductivity near interband transition energies.

Contribution

It introduces a non-perturbative theory of photon-dressed quasiparticles in 2D Dirac semiconductors, accounting for resonant interband transitions and nonequilibrium carrier kinetics, with analytic results in various relaxation regimes.

Findings

Photon-dressed quasiparticles exhibit dynamical gaps dependent on field amplitude and polarization.

Valley Hall conductivity is significantly enhanced near interband transition energies.

Analytic expressions describe valley Hall effects across different relaxation regimes.

Abstract

We present a theory of the photovoltaic valley-dependent Hall effect in a two-dimensional 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. The non-perturbative renormalization effect of the pump field manifests itself in the dynamics of the photon-dressed quasiparticles, with a quasienergy spectrum characterized by {dynamical gaps $\delta_\eta$ ($\eta$ is the valley index)} that strongly depend on field amplitude and polarization. Nonequilibrium carrier distribution functions are determined by the pump field frequency $\omega$ as well as the ratio of intraband relaxation time $\tau$ and interband recombination time $\tau_{\mathrm{rec}}$. We obtain analytic results in three regimes, when (I) all relaxation processes are negligible, (II) $\tau \ll \tau_{\mathrm{rec}}$, and (III) $\tau \gg \tau_{\mathrm{rec}}$, and display corresponding asymptotic dependences on $\delta_\eta$ and $\omega$. We then apply our theory to two-dimensional 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.