Yaroslav Tserkovnyak

Affiliations

• Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA

Title

Topological spin transport by Brownian diffusion of domain walls

Abstract

We propose thermally populated domain walls (DWs) in an easy-plane easy-axis ferromagnetic insulator as a spin transport channel between two metals. The chirality of a DW, which we call the topological charge, couples to the spin accumulation in the left metal via spin-transfer torque, which results in the charge-dependent thermal nucleation rates of DWs at the left interface. The overpopulated DWs with a particular charge diffuse by Brownian motion. A few of them leave the ferromagnet through the right interface and inject the spin current into the right metal via spin pumping. The conservation of the topological charge supports an algebraic decay of spin transport as the length of the ferromagnet increases; this is analogous to the decaying behavior of superfluid spin transport but contrasts with the exponential decay of magnon spin transport. We envision that spin transport with algebraic decay may be implemented in materials with exotic phases, such as spin ices, by exploiting topological characteristics and the associated conserved quantities of their excitations, as in the case of, e.g., spin ice monopoles.

References

• S. K. Kim, S. Takei, and Y. Tserkovnyak, Topological spin transport by Brownian diffusion of domain walls, arXiv:1507.08767.