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Spin polarization of two-dimensional electrons in GaAs quantum wells around Landau level filling nu = 1 from NMR measurements of gallium nuclei.

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Melinte, Sorin [UCL] Freytag, N Horvatic, M Berthier, C Levy, LP Bayot, Vincent [UCL] Shayegan, M.

A nuclear magnetic resonance (NMR) study has been carried out con a GaAs/Al0.3Ga0.7As multiple-quantum-well sample, containing two-dimensional (2D) electron layers, in the quantum Hall regime. The spin polarization To of 2D electrons is determined from the hyperfine shift of Ga-69,Ga-71 nuclei, measured by standard pulsed NMR. We have used the tilted-magnetic field technique to investigate the effect of an increasing Zeeman energy on To around Landau level filling factor nu =1. Mostly on the basis of measurements performed at B = 17 T and T = 1.5 K, we conjecture that in the high-B and low-T limit, P(nu) follows the predictions of the noninteracting-electron model. The low-temperature P(nu =1) is found to be far below the expected full polarization, and the observed nuclear spin-lattice relaxation rate is not reduced, in contrast to the observations by optically pumped NMR. The two techniques obtain different results only close to nu =1, and the reason why remains unclear; simple explanation in terms of the nonuniform electron density does not seem satisfactory.

Document type Article de périodique (Journal article) – Article de recherche
Publication date 2001
Language Anglais
Journal information "Physical Review B, Condensed matter and materials physics" - Vol. 64, no. 8, p. 085327 (9)
Peer reviewed yes
Publisher The American Physical Society ((United States))
issn 1098-0121
e-issn 1550-235X
Publication status Publié
Affiliation UCL - FSA/ELEC - Département d'électricité
Links
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Bibliographic reference Melinte, Sorin ; Freytag, N ; Horvatic, M ; Berthier, C ; Levy, LP ; et. al. Spin polarization of two-dimensional electrons in GaAs quantum wells around Landau level filling nu = 1 from NMR measurements of gallium nuclei.. In: Physical Review B, Condensed matter and materials physics, Vol. 64, no. 8, p. 085327 (9)
Permanent URL http://hdl.handle.net/2078.1/42549