Filling-factor-dependent electron correlations observed in cyclotron resonance - art. no. 121203

Cyclotron resonances of electron space-charge layers in GaAs were studied a t He-3 temperatures covering a density regime from 2 to 13 x 10(11) cm(-2). For densities higher than about 6 x 10(11) cm-(2) many-body influences are sufficiently reduced such that line splittings due to band-structure influ ences were involved. At integer filling factors the spin-up and spin-down e lectrons are not completely decoupled as predicted by theory. Inter Landau- level optical gaps are renormalized at odd fillings, and there is a correla tion gap between spin- and charge-density excitations in the long-wavelengt h limit.