MAGNETOOPTICS IN THE INTEGER AND FRACTIONAL QUANTUM HALL AND ELECTRON SOLID REGIMES

Emission from the recombination of two-dimensional electrons and valence band holes has been studied in the integer quantum Hall, fractional quantum Hall and electron solid regimes in ultrahigh mobility GaAs single quantum wells and single heterojunctions. At integer Hall plateaus, the polarization dependence of shifts in the electron-hole recombination energy are used to determine the mechanisms of changes in the many-body electron screening. At precisely the position of the nu = 2/3 fractional quantum Hall state, a sharp blue shift is observed, accompanied by a decrease in the upper-spin-state emission, indicating the polarized nature of the ground state. At nu = 1/3 and 2/5 a splitting in the main emission peak occurs, with the higher energy component becoming dominant at higher magnetic fields. Finally, in the regime of the electron solid, an overall decrease in the intensity is attended by a shift in spectral weight to the low energy features. However, no substantial change in the luminescence occurs between 200 and 38 mK at filling factors nu less-than-or-equal-to 1/5 while simultaneous measurement of the nonlinear transport shows a significant qualitative difference.