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Momentum effects on focusing in one-dimensional systems

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The quantisation of conductance into units of 2e2/h in a one-dimensional channel is well understood. In a high dc bias, additional features are observed at low conductances (G < 2e2/h)which have not, as yet, been fully explained. Recently it has been suggested that the presence of a feature in the region of 0.2-0.3(2e2/h) is due to polarisation of the 1D subbands by a high dc bias. Focusing measurements have been demonstrated to allow 1D channels to act as spin-filters. I will review work in related fields and then present the first investigation into the effect of the low conductance dc bias feature on focusing spectra. The device studied consists of an emitter and collector of standard measurements with an additional gate affecting the 2DEG through which electrons travel whilst focusing. There are several features of interest in the data most importantly a shift in focusing peaks with emitter conductance which is directly related to the presence of the dc bias feature. I will explain why we attribute this to a change in electron momentum direction and discuss the possibilities for further work in this area.

This talk is part of the Semiconductor Physics series.

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