Resonant tunneling-based spin ratchets

TL;DR

This paper proposes a resonant tunneling-based spin ratchet mechanism that generates directed spin-polarized currents in ac-driven quantum dot structures using local magnetic fields, with potential applications in spintronics.

Contribution

It introduces a novel spin ratchet mechanism utilizing resonant spin transfer in quantum dots with opposite Zeeman splitting, supported by numerical quantum transport calculations.

Findings

Enables nonzero average spin currents without net charge flow.

Demonstrates applicability to semiconductor nanostructures with quantum dots.

Provides numerical analysis of I-V characteristics in nonlinear regime.

Abstract

We outline a generic ratchet mechanism for creating directed spin-polarized currents in ac-driven double well or double dot structures by employing resonant spin transfer through the system engineered by local external magnetic fields. We show its applicability to semiconductor nanostructures by considering coherent transport through two coupled lateral quantum dots, where the energy levels of the two dots exhibit opposite Zeeman spin splitting. We perform numerical quantum mechanical calculations for the I-V characteristics of this system in the nonlinear regime, which requires a self-consistent treatment of the charge redistribution due to the applied finite bias. We show that this setting enables nonzero averaged net spin currents in the absence of net charge transport.