Spring 2014 Physics Colloquium
January 17; PAS 224, 3pm
Giovanni Vignale
University of Missouri-Columbia
Coupled spin-charge dynamics in semiconductors: Coulomb drag to spin Hall effect
The capability to create spin and electron-hole density gratings in semiconductors quantum wells and to probe their evolution -- diffusion
and drift -- in real time, opens new avenues to the study of coupled spin-charge dynamics of
electrons in semiconductors. In this talk I describe some of the physical effects
that have been recently observed by this technique: the spin Coulomb drag, the
electron-hole Coulomb drag, and the anomalous drift and diffusion caused by
spin-orbit interactions. I then discuss a recent theoretical prediction that an
electric field parallel to the wavefronts of an electron-hole grating in a GaAs
quantum well generates, via the electronic spin Hall effect, a spin grating of the
same wave vector. I refer to this phenomenon as "collective spin Hall effect".
A detailed study of the coupled-spin charge dynamics for quantum wells grown
in different directions reveals rich features in the time evolution of the induced
spin density, including the possibility of generating a helical spin grating from
a density grating.