Zeeman ratchets: pure spin current generation in mesoscopic conductors with non-uniform magnetic fields

TL;DR

This paper demonstrates that a quantum wire in a 2DEG with inhomogeneous magnetic fields can generate a pure spin current without charge flow when driven by an external ac voltage, using numerical Green function methods.

Contribution

It introduces a novel spin ratchet mechanism in mesoscopic conductors employing non-uniform magnetic fields and nonlinear driving, with detailed numerical analysis of different ferromagnetic stripe configurations.

Findings

Pure spin current can be generated without charge transport.

Inhomogeneous magnetic fields enable spin ratchet effects.

Numerical simulations confirm the feasibility of the proposed setup.

Abstract

We consider the possibility to employ a quantum wire realized in a two-dimensional electron gas (2DEG) as a spin ratchet. We show that a net spin current without accompanying net charge transport can be induced in the nonlinear regime by an unbiased external driving via an ac voltage applied between the contacts at the ends of the quantum wire. To achieve this we make use of the coupling of the electron spin to inhomogenous magnetic fields created by ferromagnetic stripes patterned on the semiconductor heterostructure that harbours the 2DEG. Using recursive Green function techniques we numerically study two different setups, consisting of one and two ferromagnetic stripes, respectively.