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Electrical read-out of the local nuclear polarization in the quantum Hall effect

A. Würtz·T. Müller·A. Lorke·D. Reuter·A. D. Wieck
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Abstract

It is demonstrated that the now well-established `flip-flop' mechanism of spin exchange between electrons and nuclei in the quantum Hall effect can be reversed. We use a sample geometry which utilizes separately contacted edge states to establish a local nuclear spin polarization --close to the maximum value achievable-- by driving a current between electron states of different spin orientation. When the externally applied current is switched off, the sample exhibits an output voltage of up to a few tenths of a meV, which decays with a time constant typical for the nuclear spin relaxation. The surprizing fact that a sample with a local nuclear spin polarization can act as a source of energy and that this energy is well above the nuclear Zeeman splitting is explained by a simple model which takes into account the effect of a local Overhauser shift on the edge state reconstruction.

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A. Würtz, T. Müller, A. Lorke, D. Reuter, A. D. Wieck. 2005-03-16. Electrical read-out of the local nuclear polarization in the quantum Hall effect. https://doi.org/10.1103/physrevlett.95.056802

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