Polarized currents and spatial separation of Kondo state: NRG study of spin-orbital effect in a double QD

TL;DR

This study uses numerical renormalization group analysis of a double quantum dot system to demonstrate how magnetic fields and gate voltages can induce and reverse opposing spin polarizations, revealing a spatially separated Kondo state.

Contribution

It introduces a detailed NRG analysis of spin-orbital effects in a double quantum dot, showing controllable spin polarization and spatial separation of the Kondo state.

Findings

Opposing spin polarizations can be induced by magnetic fields and gate voltages.

Polarizations can be reversed by changing gate potentials.

The Kondo peak originates from spatially separated parts of the device.

Abstract

A double quantum dot device, connected to two channels that only see each other through interdot Coulomb repulsion, is analyzed using the numerical renormalization group technique. By using a two-impurity Anderson model, and parameter values obtained from experiment [S. Amasha {\it et al.}, Phys. Rev. Lett. {\bf 110}, 046604 (2013)], it is shown that, by applying a moderate magnetic field, and adjusting the gate potential of each quantum dot, opposing spin polarizations are created in each channel. Furthermore, through a well defined change in the gate potentials, the polarizations can be reversed. This polarization effect is clearly associated to a spin-orbital Kondo state having a Kondo peak that originates from spatially separated parts of the device. This fact opens the exciting possibility of experimentally probing the internal structure of an SU(2) Kondo state.