  The phenomenon of mesoscopic Spin-Hall effect reveals in a nonequilibrium
spin accumulation (driven by electric current) at the edges of a ballistic
conductor or, more generally, in the regions with varying electron density. In
this paper we review our recent results on spin accumulation in ballistic
two-dimensional semiconductor heterostructures with Rashba/Dresselhaus spin
orbit interactions, and extend the method developed previously to predict the
existince of spin-Hall effect on the surface of three-dimensional topological
insulators. The major difference of the new Spin-Hall effect is its magnitude,
which is predicted to be much stronger than in semiconductor heterostructures.
This happens because in semiconductors the spin accumulation appears due to a
small spin-orbit interaction, while the spin-orbit constitutes a leading term
in the Hamiltonian of topological insulator.
