Crossover between two different Kondo couplings in side-coupled double quantum dots

Abstract

We study the Kondo effect in side-coupled double quantum dots with particular focus on the crossover between two distinct singlet ground states, using the numerical renormalization group. The crossover occurs as the quantized energy level of the embedded dot, which is connected directly to the leads, is varied. In the parameter region where the embedded dot becomes almost empty or doubly occupied, the local moment emerging in the other dot at the side of the path for the current is screened via a superexchange process by the conduction electrons tunneling through the embedded dot. In contrast, in the other region where the embedded dot is occupied by a single electron, the local moment emerges also in the embedded dot, and forms a singlet bond with the moment in the side dot. Furthermore, we derive two different Kondo Hamiltonians for these limits carrying out the Schrieffer-Wolff transformation, and show that they describe the essential feature of the screening for each case.

9 pages, 9 figures

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• The SU(4) Kondo effect in double quantum dots with ferromagnetic leads
• Transport through side-coupled multilevel double quantum dots in the Kondo regime
• Interplay of the Kondo effect with the induced pairing in electronic and caloric properties of T-shaped double quantum dots
• Replicas of the Fano resonances induced by phonons in a subgap Andreev tunneling
• Kondo holes in strongly correlated impurity arrays: RKKY driven Kondo screening and hole-hole interactions
• Transient dynamics of double quantum dots coupled to two reservoirs
• The PointGroupNRG code for numerical renormalization group calculations with discrete point-group symmetries
• Transport properties of proximitized double quantum dots
• Identifying an effective model for the two-stage-Kondo regime: Numerical renormalization group results
• Dynamic Transport Characteristics of Side-Coupled Double Quantum-Impurity Systems