SU(4) Fermi Liquid State and Spin Filtering in a Double Quantum Dot System

TL;DR

This paper investigates a double quantum dot system exhibiting SU(4) Fermi liquid behavior with entangled spin and charge correlations, revealing spin filtering and magneto-conductance effects under external magnetic fields.

Contribution

It demonstrates the emergence of SU(4) symmetry and spin filtering in a double quantum dot system with strong capacitive coupling, using renormalization group analysis.

Findings

SU(4) symmetric Fermi liquid state identified

Large magneto-conductance under magnetic field

Perfect spin polarization in four-lead setup

Abstract

We study a symmetrical double quantum dot (DD) system with strong capacitive inter-dot coupling using renormalization group methods. The dots are attached to separate leads, and there can be a weak tunneling between them. In the regime where there is a single electron on the DD the low-energy behavior is characterized by an SU(4)-symmetric Fermi liquid theory with entangled spin and charge Kondo correlations and a phase shift $\pi/4$. Application of an external magnetic field gives rise to a large magneto-conductance and a crossover to a purely charge Kondo state in the charge sector with SU(2) symmetry. In a four lead setup we find perfectly spin polarized transmission.