Electrically Probing Nuclear Spin Polarization in an InSb Single Quantum Well

We perform tilted-magnetic-field and resistively detected nuclear magnetic resonance (RDNMR) measurements of a symmetrically doped InSb single quantum well. Two types of Landau level crossings are presented in magnetotransport spectra by tilting the quantum well, one is characterized by a collapse of longitudinal resistance minimum and another shows resistance spikes within persistent resistance minimum. A small rf field with the frequency sweeping through the Larmor resonance of individual nuclear isotopes is applied to probe the nuclear spin polarization at or near these crosses. By flowing a relatively large current, NMR signals of high nuclear spin isotopes of both In and Sb at the resistance spikes around filling factor 2 are detected using the RDNMR measurement. We interpret this as evidence that energetically degenerate domains with different pseudospin polarization are requisite for dynamic nuclear polarization at the cross.