A proposal for time-dependent pure-spin-current generators

We propose a pure-spin-current generator based on a single level quantum dot (QD) device subjected to time-dependent magnetic fields. Under low temperature and high magnetic fields, the spin-dependent Seebeck coefficient in the transition regime is rapidly enhanced by several orders of magnitude larger than that in the steady regime. This fact is attributed to a delay effect of the electron transmission probability with respect to the split of the QD energy level. When a temperature gradient is applied across the device, the pure spin current emerges. The findings here suggest a feasible way of enhancing thermospin effects and generating the pure spin current by time-dependent external fields. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764557]