Spatial distribution of dynamically polarized nuclear spins in electron spin domains in the $ u = 2/3$ fractional quantum Hall state studied by nuclear electric resonance

Nuclear electric resonance (NER) is based on nuclear magnetic resonance mediated by spatial oscillations of electron spin domains excited by a radio frequency (RF) electric field, and it allows us to investigate the spatial distribution of the nuclear spin polarization around domain walls (DWs). Here, NER measurements were made of the dynamic nuclear spin polarization (DNP) at the spin phase transition of the fractional quantum Hall state at a Landau level filling factor of $ u=2/3$. From the RF pulse power and pulse duration dependence of the NER spectrum, we show that the DNP occurs only within $sim 100$ nm around DWs, and that it does not occur in DWs. We also show that DWs are pinned by the hyperfine field from polarized nuclear spins.