Ultraslow electron spin dynamics in the fractional quantum Hall regime

Recent optically pumped nuclear magnetic resonance (OPNMR) measurements in two different electron-doped multiple quantum well samples near the fractio nal quantum Hall ground state v=1/3 are reviewed. Below 0.5 K, the spectra provide evidence that the spin-reversed charged excitations of this ground state are localized over the NMR time scale of similar to 40 mu s. By varyi ng NMR pulse parameters, the electron spin temperature las measured by the Knight shift) could be driven above the lattice temperature. For T-lattice < 0.5 K, these non-equilibrium measurements imply that the value of the ele ctron spin-lattice relaxation time tau(1s) lies between 100 mu s and 500 ms at v=1/3. (C) 1998 Elsevier Science B.V. All rights reserved.