Edge spin accumulation in a ballistic regime
A. Khaetskii+, E. Sukhorukov*
+Institute of Microelectronics Technology, Russian Acedemy of Sciences, 142432 Chernogolovka, Moscow District, Russia
*Department of Theoretical Physics, University of Geneva, CH-1211 Geneva, Switzerland
Abstract
We consider a mesoscopic ballistic structure with Rashba
spin-orbit splitting of the electron spectrum. The ballistic region is
attached to the leads with a voltage applied between them. We calculate the
edge spin density which appears in the presence of a charge current through
the structure due to the difference in populations of electrons coming from
different leads. Combined effect of the boundary scattering and spin
precession leads to oscillations of the edge polarization with the envelope
function decaying as a power law of the distance from the boundary. The
problem is solved with the use of scattering states. The simplicity of the
method allows to gain an insight into the underlaying physics. We clarify
the role of the unitarity of scattering for the problem of edge spin
accumulation. In case of a straight boundary it leads to exact cancellation
of all long-wave oscillations of the spin density. As a result, only the
Friedel-like spin density oscillations with the momentum 2kF survive.
However, this appears to be rather exceptional case. In general, the smooth
spin oscillations with the spin precession length recover, as it happens,
e.g., for the wiggly boundary. We demonstrate also, that there is no
relation between the spin current in the bulk, which is zero in the
considered case, and the edge spin accumulation.