title: Electrical readout of the local nuclear polarization in the quantum Hall effect: a hyperfine battery.
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 mV, which decays with a time constant typical for the nuclear spin relaxation. The surprising 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.
authors.affiliation: Laboratorium für Festkörperphysik, Universität Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg, Germany. lorke@uni-duisburg.de
authors.forename: A
authors.initials: A
authors.lastname: Würtz
authors.forename: T
authors.initials: T
authors.lastname: Müller
authors.forename: A
authors.initials: A
authors.lastname: Lorke
authors.forename: D
authors.initials: D
authors.lastname: Reuter
authors.forename: A D
authors.initials: AD
authors.lastname: Wieck