Kondo effect in spin-orbit mesoscopic interferometers

TL;DR

This paper investigates how Rashba spin-orbit interaction and magnetic flux influence the Kondo effect in a mesoscopic interferometer, revealing a tunable, oscillatory effective magnetic field that affects the Kondo resonance.

Contribution

It introduces a detailed analysis of the interplay between spin-orbit coupling, magnetic flux, and electron interactions in a quantum dot system, providing a new understanding of the compensation of Kondo resonance splitting.

Findings

The Kondo resonance splitting can be compensated by an external magnetic field.

The effective magnetic field oscillates with spin-orbit and Aharonov-Bohm phases.

The effective field never vanishes due to particle-hole symmetry breaking.

Abstract

We consider a flux-threaded Aharonov-Bohm ring with an embedded quantum dot coupled to two normal leads. The local Rashba spin-orbit interaction acting on the dot electrons leads to a spin-dependent phase factor in addition to the Aharonov-Bohm phase caused by the external flux. Using the numerical renormalization group method, we find a splitting of the Kondo resonance at the Fermi level which can be compensated by an external magnetic field. To fully understand the nature of this compensation effect, we perform a scaling analysis and derive an expression for the effective magnetic field. The analysis is based on a tight-binding model which leads to an effective Anderson model with a spin-dependent density of states for the transformed lead states. We find that the effective field originates from the combined effect of Rashba interaction and magnetic flux and that it contains important corrections due to electron-electron interactions. We show that the compensating field is an oscillatory function of both the spin-orbit and the Aharonov-Bohm phases. Moreover, the effective field never vanishes due to the particle-hole symmetry breaking independently of the gate voltage.