Topological spin pumps I

Abstract

We have established a semiclassical kinetic approach for various spin correlated pumping phenomena incorporating spin rotation in wave functions into transport equations. We employ this technique to study topological pumps and illustrate spin pumping in a few models where various spin configurations or topological motors drive adiabatic pumps. In the Rashba model we find that a topological spin pump is driven by a meron with positive one half skyrmion charge, the size of which can be controlled by external gates or Zeeman fields. In the Dresselhaus model on the other hand, electron spins are pumped out by a negative meron. We examine effects of Zeeman fields on topological spin pumping and responses of fermi seas in various pumps. The phenomena of topological pumping are attributed to topological Stern-Gerlach splitting and occur in a transverse direction along which charge pumping currents either vanish or are negligible. The transport equations established here might also be applied for the studies of anomalous Hall effect and spin Hall effect as demonstrated in one of appendices.