Optically Pumped NMR Studies of Electron Spin Polarization and Dynamics: New Constraints on the Composite Fermion Description of nu = 1/2

TL;DR

This study uses optically pumped NMR to measure electron spin properties in GaAs quantum wells at filling factor 1/2, providing new constraints on composite fermion models of this quantum Hall state.

Contribution

It offers novel experimental data on electron spin polarization and dynamics near the transition between different spin-polarized states at nu=1/2.

Findings

Measured Knight shift and relaxation rates in GaAs quantum wells.

Compared experimental data with composite fermion model predictions.

Provided new constraints on theoretical descriptions of nu=1/2.

Abstract

The Knight shift and the nuclear spin-lattice relaxation rate 1/T1 of Ga-71 nuclei are measured in GaAs quantum wells at Landau level filling factor nu = 1/2 using optically pumped NMR. The temperature dependences of these data are compared with predictions of a weakly-interacting composite fermion model. Our measurements of the electron spin polarization and spin dynamics near the transition between fully and partially spin-polarized ground states provide new constraints on the theoretical description of nu = 1/2.