Semiclassical spin-spin dynamics and feedback control in transport through a quantum dot

TL;DR

This paper develops a semiclassical theory of spin-dependent transport through a quantum dot, revealing complex dynamics including oscillations and chaos, and introduces a feedback scheme for controlling spin currents.

Contribution

It introduces a nonlinear semiclassical model for spin transport in quantum dots and demonstrates feedback control for spin filtering and current manipulation.

Findings

Discovery of self-sustained oscillations and chaos in spin dynamics.

Implementation of a feedback scheme to control spin-dependent currents.

Potential for spin filtering and transport against bias using feedback.

Abstract

We present a theory of magnetotransport through an electronic orbital, where the electron spin interacts with a (sufficiently) large external spin via an exchange interaction. Using a semiclassical approximation, we derive a set of equations of motions for the electron density matrix and the mean value of the external spin that turns out to be highly nonlinear. The dissipation via the electronic leads is implemented in terms of a quantum master equation that is combined with the nonlinear terms of the spin-spin interaction. With an anisotropic exchange coupling a variety of dynamics is generated, such as self-sustained oscillations with parametric resonances or even chaotic behavior. Within our theory we can integrate a Maxwell-demon-like closed-loop feedback scheme that is capable of transporting particles against an applied bias voltage and that can be used to implement a spin filter to generate spin-dependent oscillating currents of opposite directions.