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

Abstract

We use cotunneling spectroscopy to investigate spin, orbital, and spin-orbital Kondo transport in a strongly confined system of InAs double quantum dots that are 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 interdot 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.