Generating voltage and suppressing spin transport by an Inverse Stern-Gerlach Effect in semiconductors

The discovery of spin relied on spin separation by a magnetic field gradient; this mechanism has received little attention as a means for generating spin and charge currents in semiconductors. We derive a set of coupled spin-charge drift-diffusion equations to show that magnetic field gradients can be used to generate charge currents from non-equilibrium spin polarization. We predict, in GaAs, an “Stern-Gerlach” voltage comparable to what is measured by the inverse spin Hall effect. Non-intuitively, we find the spin diffusion length is reduced by the magnetic gradient. This is understood by invoking the idea of co-current and counter-current exchange which is a concept appearing in the fields of animal physiology and thermal engineering.

[1] N. J. Harmon, E. Z. Kurth, D. Coleman, L. Flanigan, arXiv:2307.16838