SPIN-FLIP EXCITATIONS IN THE FRACTIONAL-QUANTUM-HALL-EFFECT REGIME STUDIED BY POLARIZED PHOTOLUMINESCENCE OF CHARGED EXCITONS

摘要

We report on a tow-temperature magneto-optical study of the spin-singlet charged exciton (X-s(-)) transitions in GaAs/Al0.1Ga0.9As modulation-doped multiple quantum wells with an optically tuned two-dimensional electron gas (2DEG) density corresponding to a filling factor in the range 0 < nu less than or equal to 1. We find strong evidence for the effect of 2DEG magnetic correlations on the X-s(-) spin-resolved transitions. The energy difference between the sigma(-)- and sigma(+)-polarized X-s(-) photoluminescence (PL) intensity maxima is found to oscillate with varying nu. The numerical derivative of these oscillations with respect to nu shows minima at odd denominator rational fractions and maxima at even denominator fractions, similar to the longitudinal resistivity measured in the fractional quantum Hall effect. At nu = 1, the observed sigma(-)-polarized low-energy PL tail is interpreted (by a line-shape analysis) to be due to a finite-k 2DEG spin-wave emission coupled to the optical recombination of the X-s(-). [References: 28]