Spintronic transport and Kondo effect in quantum dots

TL;DR

This paper explores how ferromagnetic leads influence spin-dependent transport and Kondo correlations in quantum dots, revealing effects on local density of states, shot noise, and potential future research directions.

Contribution

It provides a detailed analysis of the impact of ferromagnetic lead coupling on Kondo physics in quantum dots, including numerical and perturbative approaches.

Findings

Fano factor suppressed below Poissonian limit at symmetric point

Influence of ferromagnetic leads depends on charge fluctuations

Potential extensions include magnon coupling and multi-dot systems

Abstract

We investigate the spin-dependent transport properties of quantum-dot based structures where Kondo correlations dominate the electronic dynamics. The coupling to ferromagnetic leads with parallel magnetizations is known to give rise to nontrivial effects in the local density of states of a single quantum dot. We show that this influence strongly depends on whether charge fluctuations are present or absent in the dot. This result is confirmed with numerical renormalization group calculations and perturbation theory in the on-site interaction. In the Fermi-liquid fixed point, we determine the correlations of the electric current at zero temperature (shot noise) and demonstrate that the Fano factor is suppressed below the Poissonian limit for the symmetric point of the Anderson Hamiltonian even for nonzero lead magnetizations. We discuss possible avenues of future research in this field: coupling to the low energy excitations of the ferromagnets (magnons), extension to double quantum dot systems with interdot antiferromagnetic interaction and effect of spin-polarized currents on higher symmetry Kondo states such as SU(4).