Figure 1

Conductivity change $\Delta {\sigma }_{xx}/{\sigma }_{xx}$ vs the tuning field $E_{\perp }$ for the surface density $n_s=4.0\times {10}^7{\mathrm{cm}}^{-2}$ at $T=0.4\mathrm{K}$. Solid lines are traces obtained in an upward sweep. Corresponding to their increasing amplitude, the traces were taken at MW power $P=40$, 130, 380 and $1000\mu \mathrm{W}$. The dashed line is the trace taken in a downward sweep at $P=1000\mu \mathrm{W}$ (the sweeping directions are indicated by arrows).Reuse & Permissions

Figure 2

Frequency shift $\Delta {\omega }_C/2\pi$ vs electron temperature $T_e$ obtained from the measured resonant response (squares). The solid line is given by Eq. (2) with $F=8.91$.Reuse & Permissions

Figure 3

Resonant response for $n_s=8.0\times {10}^6{\mathrm{cm}}^{-2}$ at $T=0.2\mathrm{K}$ obtained in an upward (open squares) and downward (solid squares) sweeps with $P=870\mu \mathrm{W}$. The sweeping directions are indicated by arrows.Reuse & Permissions

Figure 4

Graphical solutions of the energy balance Eq. (3) for $n_s=4.0\times {10}^7{\mathrm{cm}}^{-2}$ and $T=0.4\mathrm{K}$. The solid line shows the cooling rate ${\nu }_E{k}_B(T_e-T)$. The dashed lines show the heating rate $\hslash \omega r({\rho }_{11}-{\rho }_{22})$ calculated for three frequency detunings ${\omega }_{21}-\omega ={\delta }_1$, ${\delta }_{\mathrm{bi}}$ and ${\delta }_2$ ($-1.15$, $-0.85$ and $-0.7\mathrm{GHz}$, respectively). The other parameters are ${\Omega }_R/2\pi =0.01\mathrm{GHz}$, $\gamma /2\pi =0.2\mathrm{GHz}$ and $\omega /2\pi =104.5\mathrm{GHz}$. The circles mark two stable solutions of Eq. (3) for detuning ${\delta }_{\mathrm{bi}}$. Inset: $T_e$ vs $E_{\perp }$ and $\delta$ calculated from Eq. (3) for the same $n_s$, $T$, ${\Omega }_R$ $\gamma$, and $\omega$. The high- and low-$T_e$ branches are plotted by the solid lines, the dashed arrows indicate interbranch switching.Reuse & Permissions