Oscillatory ac conductivity and photoconductivity of a two-dimensional electron gas: Quasiclassical transport beyond the Boltzmann equation

We have analyzed the quasiclassical mechanism of magneto-oscillations in the ac conductivity and photoconductivity, related to non-Markovian dynamics of disorder-induced electron scattering. While the magneto-oscillations in the photoconductivity are found to be weak, the effect manifests itself much more strongly in the ac conductivity, where it may easily dominate over the oscillations due to the Landau quantization. We argue that the damping of the oscillatory photoconductivity provides a reliable method of measuring the homogeneous broadening of Landau levels (single-particle scattering rate) in high-mobility structures.

Figure 1

Graphic representation of various contributions to the photoconductivity [Eqs. (2, 3)] in the $(\nu ,n)$ space at the lowest order ${\sigma }_{\mathrm{ph}}\sim \mathcal{O}\left({\mathcal{E}}_{\mathrm{dc}}^0{\mathcal{E}}_{\omega }^2\right)$.

Figure 2

Diagrams describing the memory effects in the photoconductivity ${\sigma }_{\mathrm{ph}}$: oscillatory self-energy (b) and vertex (c) corrections to the smooth part (a) of ${\sigma }_{\mathrm{ph}}$.

Figure 3

Quasiclassical [${\sigma }_{\omega }^{\left(c\right)}$, Eq. (40)] and quantum [${\sigma }_{\omega }^{\left(q\right)}$, Eq. (41)] oscillatory ac conductivity (normalized to the Drude conductivity ${\sigma }_{\omega }^{\mathrm{D}}$) vs ${\omega }_c∕\omega$ for $\omega ∕2\pi =100\mathrm{GHz}$, $\tau =0.6\mathrm{ns}$, $\tau ∕{\tau }_q=50$, ${\tau }_S∕{\tau }_L=0.1$, $a∕\delta =0.25$ at ${\omega }_c∕\omega =1∕2$.