Electronic states in gallium arsenide quantum wells probed by optically pumped NMR.

摘要: An optical pumping technique was used to enhance and localize nuclear magnetic resonance (NMR) signals from an n-doped GaAs/Al0.1Ga0.9As multiple quantum well structure, permitting direct radio-frequency measurements of gallium-71 NMR spectra spin-lattice relaxation rates (1/T1) as functions temperature (1.6 K < T 4.2 K) the Landau level filling factor (0.66 v 1.76). The reveal effects electron-electron interactions on energy levels spin states two-dimensional electron system confined in GaAs wells. Minima 1/T1 at approximately 1 2/3 indicate gaps for electronic excitations both integer fractional Hall states. Rapid, temperature-independent intermediate values indicates a manifold low-lying with mixed polarizations.