Optical Anomalies of the Two-Dimensional Electron Gas in the Extreme Magnetic Quantum Limit

Abstract

Band-gap optical recombination from the two-dimensional electron gas in GaAs-(Al,Ga)As quantum wells was measured in the regime of the fractional quantum Hall effect. New intrinsic emission lines emerge at the Landau-level filling factor $\ensuremath{\nu}\ensuremath{\lesssim}1$ and at $\ensuremath{\nu}<0.8$. The anomaly near $\ensuremath{\nu}=1$ is associated with changes in population of the lowest spin-split Landau level. The spectral doublet observed near $\ensuremath{\nu}=\frac{2}{3}$ has a striking temperature dependence below $T=2$ K similar to the magnetoresistance ${\ensuremath{\rho}}_{\mathrm{xx}}$ associated with the many-body quantum fluid.