Real-Space Approach to Light-Induced Hall Transport in Disordered Materials

Abstract

We introduce a linear-scaling real-space methodology to compute time-resolved electrical responses of materials driven far-from-equilibrium, with energy relaxation and disorder treated on equal footing. Applying this approach to AB-stacked (Bernal) bilayer graphene, driven by a circularly polarized optical pulse, we observe the generation of a finite Hall conductivity. This Hall signal oscillates during optical driving and remains sizable after the light is switched off before relaxing toward equilibrium. Remarkably, this dynamical Hall response is robust in the presence of realistic descriptions of disorder, suggesting that disorder and relaxation dynamics can be leveraged as design parameters rather than being limitations. More broadly, our new methodology enables the investigation of electrical responses in driven, complex disordered quantum materials and highlights how engineered energy transfer pathways can enable ultrafast optoelectronic functionality.

Figures (3)

• Figure 1: Schematic of light-induced quantum transport in disordered graphene, via the valley-selective excitation of carriers from the positive-Berry-curvature valence band to the negative-Berry-curvature conduction band.
• Figure 2: a) Number of carriers multiplied by the density of states for $\mu=0$. The blue line represents the equilibrium case, and the red solid (dashed) line shows the non-equilibrium regime after optical excitation for carrier thermalization time $\tau_\mathrm{ee}= 25$ fs ($\tau_\mathrm{ee} \to \infty$). b) Hall conductivity of BLG as a function of the chemical potential in equilibrium (blue line) and after optical excitation (red lines).
• Figure 3: a) Time dependence of the applied light pulse in gray, and the Hall conductivity in red, green, and yellow for the clean system, extended electron-hole puddles, and localized electron-hole puddles, respectively, at $\mu = 0$. b) Number of excited carriers for the different systems. c) Fourier transform of the time-dependent conductivity, with the frequency in units of the pulse frequency.