Spin-orbit interaction and asymmetry effects on Kondo ridges at finite magnetic field

TL;DR

This paper investigates how spin-orbit interaction and asymmetry influence Kondo ridges in a double quantum dot system under magnetic field, revealing robustness of zero-field Kondo effects and fragility of finite-field Kondo features.

Contribution

It provides a detailed analysis of the interplay between spin-orbit coupling, magnetic field, and asymmetry effects on Kondo ridges in double quantum dots, highlighting conditions for their stability and symmetry breaking.

Findings

Zero-field Kondo ridges are robust against SOI due to time-reversal symmetry.

Finite magnetic field induces additional Kondo plateaus that vanish with SOI.

Asymmetries cause bending of Kondo ridges and require B tuning for level renormalization.

Abstract

We study electron transport through a serial double quantum dot with Rashba spin-orbit interaction (SOI) and Zeeman field of amplitude B in presence of local Coulomb repulsion. The linear conductance as a function of a gate voltage Vg equally shifting the levels on both dots shows two B=0 Kondo ridges which are robust against SOI as time-reversal symmetry is preserved. Resulting from the crossing of a spin-up and a spin-down level at vanishing SOI two additional Kondo plateaus appear at finite B. They are not protected by symmetry and rapidly vanish if the SOI is turned on. Left-right asymmetric level-lead couplings and detuned on-site energies lead to a simultaneous breaking of left-right and bonding-anti-bonding state symmetry. In this case the finite-B Kondo ridges in the Vg-B plane are bent with respect to the Vg-axis. For the Kondo ridge to develop different level renormalizations must be compensated by adjusting B.