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.
Highlights
The Kondo effect is a widely studied many-body phenomenon that has increased the understanding of strongly correlated electron systems
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
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
Summary
The Kondo effect is a widely studied many-body phenomenon that has increased the understanding of strongly correlated electron systems It can be investigated using quantum dots (QDs) with highly transparent tunnel barriers and manifests as a zero-bias conductance resonance. An alternative approach is to fabricate two parallel-coupled QDs for which the orbitals can be tuned independently This is realized in two-dimensional electron gases [17,26,27,28,29,30], but at the expense of limited Zeeman splitting of spin states. The energy gap of the avoided crossing can only be resolved if the spin degeneracy is lifted This underlines the importance of isolating different Kondo mechanisms when studying their contribution to Kondo effects of higher symmetry.
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