Electron-magnon coupling and nonlinear tunneling transport in magnetic nanoparticles

TL;DR

This paper develops a theoretical model for electron tunneling in ferromagnetic nanoparticles, revealing complex conductance features due to electron-magnon interactions that align with recent experimental observations.

Contribution

It introduces a rate-equation based theory capturing electron-magnon coupling effects on nonlinear tunneling in magnetic nanoparticles, aligning with experimental data.

Findings

Tunneling conductance shows dense resonances at strong coupling.

Resonance slopes in magnetic field are linear and of the same sign.

Model agrees with recent tunneling experiments.

Abstract

We present a theory of single-electron tunneling transport through a ferromagnetic nanoparticle in which particle-hole excitations are coupled to spin collective modes. The model employed to describe the interaction between quasiparticles and collective excitations captures the salient features of a recent microscopic study. Our analysis of nonlinear quantum transport in the regime of weak coupling to the external electrodes is based on a rate-equation formalism for the nonequilibrium occupation probability of the nanoparticle many-body states. For strong electron-boson coupling, we find that the tunneling conductance as a function of bias voltage is characterized by a large and dense set of resonances. Their magnetic field dependence in the large-field regime is linear, with slopes of the same sign. Both features are in agreement with recent tunneling experiments.