The SU(4) Kondo effect in double quantum dots with ferromagnetic leads

TL;DR

This paper explores how ferromagnetic leads influence the SU(4) Kondo effect in double quantum dots, revealing the suppression and crossover of Kondo states depending on magnetic configurations and lead polarization.

Contribution

It provides a detailed analysis of the transition from SU(4) to orbital-SU(2) Kondo states driven by lead polarization using analytical and numerical renormalization group methods.

Findings

Transport behavior depends on magnetic configuration.

Finite spin polarization induces a crossover from SU(4) to orbital-SU(2) Kondo state.

Kondo temperature exhibits non-monotonic dependence on lead polarization.

Abstract

We investigate the spin-resolved transport properties, such as the linear conductance and the tunnel magnetoresistance, of a double quantum dot device attached to ferromagnetic leads and look for signatures of SU(4) symmetry in the Kondo regime. We show that the transport behavior greatly depends on the magnetic configuration of the device, and the spin-SU(2) as well as the orbital and spin-SU(4) Kondo effects become generally suppressed when the magnetic configuration of the leads varies from the antiparallel to the parallel one. Furthermore, a finite spin polarization of the leads lifts the spin degeneracy and drives the system from the SU(4) to an orbital-SU(2) Kondo state. We analyze in detail the crossover and show that the Kondo temperature between the two fixed points has a non-monotonic dependence on the degree of spin polarization of the leads. In terms of methods used, we characterize transport by using a combination of analytical and numerical renormalization group approaches.