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Abstract

Semiconductors are ubiquitous in device electronics, because
their charge distributions can be conveniently manipulated with
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
both information processing and the study of fundamental solid-
state physics issues. Here we report procedures that carry 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.