NMR study of the electron spin polarization in the fractional quantum Hall effect of a single quantum well: Spectroscopic evidence for domain formation

Abstract

The authors have developed a technique to determine the electron spin polarization in a single GaAs quantum well by combining resistance-detected (RD) nuclear magnetic resonance (NMR) with conventional NMR. We use this method to study the unpolarized-polarized spin transition at filling factor $\ensuremath{\nu}=2∕3$ for small and large currents. The formation of domains with these two polarizations at the transition was observed spectroscopically. Domains with full, partial, or no polarization were also uncovered at $\ensuremath{\nu}=3∕5$ and $4∕7$. An anomalous NMR line shape around filling factor $\ensuremath{\nu}=1∕3$, 1, and $2∕3$ was measured. This pecularity of the NMR line is probably not due to skyrmions, as previously reported for $\ensuremath{\nu}=1$.