Spin generation away from boundaries by nonlinear transport

In several situations of interest, spin polarization may be generated farfrom the boundaries of a sample by nonlinear effects of an electric current,even when such a generation is forbidden by symmetry in the linear regime. Wepresent an analytically solvable model where spin accumulation results from acombination of current gradients, nonlinearity, and cubic anisotropy. Further,we show that even with isotropic conductivity, nonlinear effects in a lowsymmetry geometry can generate spin polarization far away from boundaries.Finally, we find that drift from the boundaries results in spin polarizationpatterns that dominate in recent experiments on GaAs by Sih et al. [Phys. Rev.Lett. 97, 096605 (2006)]