Emergent SU(4) Kondo physics in a spin–charge-entangled double quantum dot

Abstract

Quantum impurity models, which describe how a local degree of freedom interacts with a continuum, are central to condensed-matter physics. Such models may be naturally implemented with quantum dots coupled to each other and to metallic leads. Here we detail a many-body Kondo state occurring when two quantum dots are coupled electrostatically. We use orbital state-resolved bias spectroscopy to demonstrate the entanglement of spin and charge between spatially separated orbitals of the Kondo state. Detailed agreement between transport measurements and numerical renormalization group calculations suggests an emergent SU(4) symmetry.

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Figure 1: Survey of conductance at orbital degeneracies.
Figure 2: Agreement between experimental data and NRG calculations.
Figure 3: Universal scaling of the conductance.
Figure 4: Orbital state-resolved bias spectroscopy of the SU(4) Kondo resonance.

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Acknowledgements

We are grateful to Y. Oreg, A. Carmi, J. König, A. G. Moghaddam, G. B. Martins, C. A. Büsser, A. E. Feiguin, J. Bauer, A. C. Hewson and L. Peeters for discussions. Experimental work was supported by the NSF under DMR-0906062, by the US–Israel BSF grant No. 2008149, and most recently by the Gordon and Betty Moore Foundation through Grant GBMF3429. A.J.K. acknowledges a Stanford Graduate Fellowship. G.Z. and C.P.M. acknowledge support from Hungarian Grant Nos. K105149 and CNK80991. C.P.M. was financially supported by UEFISCDI under French-Romanian Grant DYMESYS, Contract No. PN-II-ID-JRP-2011-1. I.W. acknowledges support from EU grant No. CIG-303 689 and MSHE grant No. IP2011 059471. NRG calculations were performed at Poznań Supercomputing and Networking Center.

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A.J.K., S.A., G.Z. and D.G-G. designed the experiment. A.J.K. and S.A. performed the measurements, with substantial contributions from I.G.R. I.W., C.P.M. and G.Z. performed the NRG calculations. C.P.M. and I.W. contributed equally to the theoretical analysis. A.J.K., S.A., C.P.M., I.W., G.Z. and D.G-G. analysed the data. S.A. designed and fabricated the devices, with electron-beam lithography done by J.A.K., using heterostructures grown by H.S. A.J.K. wrote the paper with critical review provided by all other authors.

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Correspondence to D. Goldhaber-Gordon.

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Keller, A., Amasha, S., Weymann, I. et al. Emergent SU(4) Kondo physics in a spin–charge-entangled double quantum dot. Nature Phys 10, 145–150 (2014). https://doi.org/10.1038/nphys2844

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