Quantum kinetic theory of spin-transfer torque and magnon-assisted transport in nanostructures

TL;DR

This paper develops a quantum kinetic theory to understand how spin fluctuations influence charge transport in magnetic nanostructures, highlighting magnon-assisted transport and spin-transfer torque effects.

Contribution

It introduces a systematic quantum model capturing the interplay of charge and spin dynamics, including quantum scattering effects at low temperatures.

Findings

Magnon-assisted transport contributes to nonlinear current behavior.

Spin-transfer torque affects magnetoconductance via magnetic misalignment.

Quantum scattering signatures distinguish from thermal fluctuations at low temperatures.

Abstract

We theoretically investigate the role of spin fluctuations in charge transport through a magnetic junction. Motivated by recent experiments that measure a nonlinear dependence of the current on electrical bias, we develop a systematic understanding of the interplay of charge and spin dynamics in nanoscale magnetic junctions. Our model captures two distinct features arising from these fluctuations: magnon-assisted transport and the effect of spin-transfer torque on the magnetoconductance. The latter stems from magnetic misalignment in the junction induced by spin-current fluctuations. As the temperature is lowered, inelastic quantum scattering takes over thermal fluctuations, exhibiting signatures that make it readily distinguishable from magnon-assisted transport.