We studied spatially-resolved measurements of dynamic nuclear spin polarization (DNP) in the \(\nu =2/3\) fractional quantum Hall state. To avoid the influence of quantum Hall edge effects and to perform spatially-resolved measurements of bulk DNP alone, we fabricated a device with a multiply-connected Corbino geometry from a high-mobility GaAs/AlGaAs two-dimensional electron system wafer. We simultaneously measured six sets of resistances to track their time evolution during the depolarization, DNP, and relaxation processes. DNP was induced using large alternating or direct currents, and the polarization was carried out in the polarized phase. Under AC DNP, only monotonic changes in resistance were observed during the DNP process, whereas under DC DNP, non-monotonic behavior was detected, first decreasing (increasing) and then turning into increasing (decreasing) stage a few thousand seconds after starting the DNP, and showing random fluctuations in the latter stage. The results are consistent with our previous measurements performed in a Hall bar. Comparison of the resistances measured with different pairs of electrodes reveals that the resistance induced by domain wall mainly increase around the area close to the inner (source) electrode, with the area being smaller for DC DNP.
