Theory of Non-Coherent Spin Pumps

TL;DR

This paper develops a theoretical framework for non-coherent spin pumps, showing how classical effects can generate pure spin currents without interference, with potential experimental realization in GaAs heterostructures.

Contribution

It introduces a new theory for non-coherent spin pumping that accounts for exchange interactions and external parameter variations, enabling pure spin current generation.

Findings

Dephasing diminishes quantum interference effects.

Classical contributions to charge and spin pumping remain unaffected by dephasing.

Pure spin currents can be generated using exchange interactions and periodic gate potentials.

Abstract

We study electron pumps in the absence of interference effects paying attention to the spin degree of freedom. Electron-electron exchange interactions combined with a variation of external parameters, such as magnetic field and gate potentials, affect the compressibility-spin-tensor whose components determine the non-coherent parts of the charge and spin pumped currents. An appropriate choice of the trajectory in the parameter space generates an arbitrary ratio of spin to charge pumped currents. After showing that the addition of dephasing leads to a full quantum coherent system diminishes the interference contribution, but leaves the non-coherent (classical) contribution intact, we apply the theory of the classical term for several examples. We show that when exchange interactions are included one can construct a source of pure spin current, with a constant magnetic field and a periodic variation of gate potentials only. We discuss the possibility to observe it experimentally in GaAs heterostructures.