Sensitive detection of potential fluctuations in semiconductor two-dimensional electron system by spin polarization imaging technique

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We tried to evaluate the electron density fluctuation and the spatial profile in high quality two-dimensional electron systems by means of the magneto-optical Kerr effect at quantum Hall plateau condition. At the quantum Hall plateau, the bare potential fluctuation appears due to the absence of potential screening by electrons. The observation of electron spin polarization at quantum Hall plateau by the Kerr effect microscope is very sensitive to the local electron density, which reveals the true potential fluctuations less than 0.1%. We also confirmed that the mono-atomic layer thickness fluctuation in quantum well can be detected by the magneto-optical Kerr effect (circular dichroic absorption) and is able to map with the electron density fluctuation.