Abstract

Spintronics is the research field that aims at using electron spins as a
functional part of an electronic device. If spintronics should become
practical for building logic devices, spin polarization must be
controllable, preferentially employing electric gates. However, an electric
field does not couple directly to an electron spin. We investigate two
approaches that nevertheless allow the manipulation of spins. The first one
makes use of a strongly inhomogeneous magnetic field in which the electrons
are spatially displaced by the electric field. The second one relies on
spin-orbit interaction, where a moving electron experiences the electric
field present in the semiconductor crystal as a magnetic field. Using
time-resolved Faraday-rotation measurements of coherent spin dynamics, we
investigate such electrical spin manipulation in GaAs/InGaAs quantum wells
and find strong tunability of the spin precession frequency between
interdigitated Fe stripes. The spin-orbit coupling leads to a change in
spin precession frequency as a function of the direction of the in-plane
drift momentum. Contributions from structure inversion asymmetry and bulk
inversion asymmetry are separated and absolute values for both terms are
measured.