Imaging of electron spin polarization in quantum Hall states investigated by Kerr rotation microscopy

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The spin-related phenomena observed in the quantum Hall (QH) effect, such as the QH ferromagnet at the filling factor of Landau level ν=1, dynamic nuclear polarization by the QH breakdown current, etc., affect to the spin dynamics and also to the current distribution in the QH devices, showing the 'spin texture'. We developed an optical fiber-based Kerr microscope operating in the low temperatures below 2 K and high magnetic fields up to 9 T. The spatial resolution of 4 μm can be obtained in the QH regime. We obtained the spatial distribution image of the local filling factor through the degree of the spin polarization, and also observed the spin polarized quantum Hall current both in the bulk and near the edge areas. We are trying to set our Kerr microscope in a dilution refrigerator to investigate the spin polarization in the fractional quantum Hall regime.