Signatures of quantum phase transitions in parallel quantum dots: Crossover from local-moment to underscreened spin-1 Kondo physics

Abstract

We study a strongly interacting "quantum dot 1" and a weakly interacting "dot 2" connected in parallel to metallic leads. Gate voltages can drive the system between Kondo-quenched and non-Kondo free-moment phases separated by Kosterlitz-Thouless quantum phase transitions. Away from the immediate vicinity of the quantum phase transitions, the physical properties retain signatures of first-order transitions found previously to arise when dot 2 is strictly noninteracting. As interactions in dot 2 become stronger relative to the dot-lead coupling, the free moment in the non-Kondo phase evolves smoothly from an isolated spin-one-half in dot 1 to a many-body doublet arising from the incomplete Kondo compensation by the leads of a combined dot spin-one. These limits, which feature very different spin correlations between dot and lead electrons, can be distinguished by weak-bias conductance measurements performed at finite temperatures.

7 pages, 7 figures. Accepted for publication in Phys. Rev. B

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Cited by in corpus (7)

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• Kondo effect in graphene with Rashba spin-orbit coupling
• Spin-orbital and spin Kondo effects in parallel coupled quantum dots
• Quantum phase transitions in a pseudogap Anderson-Holstein model
• Zero-field splitting of the Kondo resonance and quantum criticality in triple quantum dots
• Functional renormalization group study of parallel double quantum dots: Effects of asymmetric dot-lead couplings
• On the competition between the Kondo effect and the exchange interaction in a parallel double quantum dot system