Selective tuning of spin-orbital Kondo contributions in parallel-coupled quantum dots

TL;DR

This study investigates spin, orbital, and spin-orbital Kondo effects in parallel-coupled InAs double quantum dots, demonstrating how to isolate and control different Kondo contributions through tuning of system parameters.

Contribution

The paper introduces a method to selectively tune and distinguish spin and orbital Kondo effects in quantum dot systems using co-tunneling spectroscopy.

Findings

Spin-orbital Kondo effect appears at orbital degeneracy without magnetic field.

Individual Kondo contributions can be isolated via orbital detuning or spin splitting.

Lifting spin degeneracy reveals orbital degeneracy and hybridization gap.

Abstract

We use co-tunneling spectroscopy to investigate spin-, orbital-, and spin-orbital Kondo transport in a strongly confined system of InAs double quantum dots (QDs) parallel-coupled to source and drain. In the one-electron transport regime, the higher symmetry spin-orbital Kondo effect manifests at orbital degeneracy and no external magnetic field. We then proceed to show that the individual Kondo contributions can be isolated and studied separately; either by orbital detuning in the case of spin-Kondo transport, or by spin splitting in the case of orbital Kondo transport. By varying the inter-dot tunnel coupling, we show that lifting of the spin degeneracy is key to confirming the presence of an orbital degeneracy, and to detecting a small orbital hybridization gap. Finally, in the two-electron regime, we show that the presence of a spin-triplet ground state results in spin-Kondo transport at zero magnetic field.