Ultraslow Electron Spin Dynamics in GaAs Quantum Wells Probed by Optically Pumped NMR

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Science  31 Jul 1998:
Vol. 281, Issue 5377, pp. 686-690
DOI: 10.1126/science.281.5377.686

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Optically pumped nuclear magnetic resonance (OPNMR) measurements were performed in two different electron-doped multiple quantum well samples near the fractional quantum Hall effect ground state ν = 1/3. Below 0.5 kelvin, the spectra provide evidence that spin-reversed charged excitations of the ν = 1/3 ground state are localized over the NMR time scale of about 40 microseconds. Furthermore, by varying NMR pulse parameters, the electron spin temperature (as measured by the Knight shift) could be driven above the lattice temperature, which shows that the value of the electron spin–lattice relaxation time τ1s is between 100 microseconds and 500 milliseconds at ν = 1/3.

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