Theory of microwave-induced oscillations in the magnetoconductivity of a two-dimensional electron gas

We develop a theory of magneto-oscillations in the photoconductivity of a two-dimensional electron gas observed in recent experiments. The effect is governed by a change of the electron distribution function induced by the microwave radiation. We analyze a nonlinearity with respect to both the dc field and the microwave power, as well as the temperature dependence determined by the inelastic relaxation rate.

Figure 1

(Color online) Schematic behavior of the oscillatory density of states $\nu \left(\epsilon \right)$ and radiation induced oscillations in the distribution function $f\left(\epsilon \right)$ for $\sin (2\pi \omega ∕{\omega }_c)>0$.

Figure 2

Photoresistivity (normalized to the dark Drude value) for overlapping Landau levels vs ${\omega }_c∕\omega$ at fixed $\omega {\tau }_q=2\pi$. The curves correspond to different levels of microwave power ${\mathcal{P}}_{\omega }^{\left(0\right)}=\{0.24,0.8,2.4\}$. Nonlinear $I\text{−}V$ characteristics at the marked minima are shown in Fig. 3.

Figure 3

Current-voltage characteristics [dimensionless current ${\tilde{j}}_x=({\sigma }_{\mathrm{ph}}∕{\sigma }_{\mathrm{dc}}^D){\tilde{\mathcal{E}}}_{\mathrm{dc}}$ vs dimensionless field ${\tilde{\mathcal{E}}}_{\mathrm{dc}}={\mathcal{Q}}_{\mathrm{dc}}^{1∕2}$] at the points of minima marked by the circles in Fig. 1. The arrows show the dc field ${\tilde{\mathcal{E}}}_{\mathrm{dc}}^{*}$ in spontaneously formed domains.

Figure 4

Photoresistivity (normalized to the dark Drude value) for separated Landau levels vs ${\omega }_c∕\omega$ at fixed $\omega {\tau }_q=16\pi$. The curves correspond to different levels of microwave power ${\mathcal{P}}_{\omega }^{\left(0\right)}=\{0.01,0.03,0.05\}$.