Electronic states in gallium arsenide quantum wells probed by optically pumped NMR.
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 and nuclear spin-lattice relaxation rates (1/T1) as functions of temperature (1.6 K < T < 4.2 K) and the Landau level filling factor (0.66 < v < 1.76). The measurements reveal effects of electron-electron interactions on the energy levels and spin states of the two-dimensional electron system confined in the GaAs wells. Minima in 1/T1 at v approximately 1 and v approximately 2/3 indicate energy gaps for electronic excitations in both integer and fractional quantum Hall states. Rapid, temperature-independent relaxation at intermediate v values indicates a manifold of low-lying electronic states with mixed spin polarizations.
Tycko
R
R
AT&T Bell Laboratories, Murray Hill, NJ 07974, USA.
Barrett
S E
SE
Dabbagh
G
G
Pfeiffer
L N
LN
West
K W
KW
D001152:Arsenicals / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004583:Electrons; D005708:Gallium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013696:Temperature
D001152:Arsenicals; C043055:gallium arsenide; D005708:Gallium