Edge magnetoplasmon in gated and ungated samples

Edge magnetoplasmon (EMP) is a collective charge oscillation in edge channels. Since the velocity of EMPs depends on their transverse width, its measurement is useful to investigate the structure of edge channels. In this work, we carried out time-of-flight measurements of EMPs using samples with and without the top gate. With the analyses of the measured velocity, we show that the transverse width of EMPs in the ungated sample is about 2 μm determined by the potential profile in the edge region. In the gated sample, on the other hand, the width oscillates between 0.3 and 3 μm with filling factor, reflecting the detailed structure of edge channels. We also find that scattering of EMPs by the bulk electrons is modified by the presence of the gate.
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Results of the time-of-flight measurement of EMPs for the samples (left panel) without the top gate and (right panel) with the top gate. In the ungated sample, the time-of-flight linearly increases with magnetic field, while, in the gated sample, it oscillates with filling factor.