Gate-voltage control of spin interactions between electrons and nuclei in a semiconductor

Semiconductors are ubiquitous in device electronics, because their charge distributions can be conveniently manipulated with applied voltages to perform logic operations, Achieving a similar level of control over the spin degrees of freedom, either from electrons or nuclei, could provide intriguing prospects for information processing and fundamental solid- state physics issues. Here, we report procedures that cam, out the controlled transfer of spin angular momentum between electrons-confined to two dimensions and subjected to a perpendicular magnetic field-and the nuclei of the host semiconductor, using gate voltages only. We show that the spin transfer rate can be enhanced near a ferromagnetic ground state of the electron system. and that the induced nuclear spin polarization can be subsequently stored and 'read-out'. These techniques can also be combined into a spectroscopic tool to detect the low-energy collective excitations in the electron system that promote the spin transfer, The existence of such excitations is contingent on appropriate electron-electron correlations, and these can be tuned by changing, for example. the electron density via a gate voltage. (C) 2002 Published by Elsevier Science B.V