Kondo effects in a triangular triple quantum dot: NRG study in the whole region of the electron filling

Abstract

We study the low-energy properties of a triangular triple quantum dot connected to two non-interacting leads in a wide parameter range, using the numerical renormalization group (NRG). Various kinds of Kondo effects take place in this system depending on the electron filling N_{tot}, or the level position ${\epsilon }_d$ of the triple dot. The SU(4) Kondo behavior is seen in the half-filled case N_{tot} = 3.0 at the dip of the series conductance, and it causes a charge redistribution between the even and odd orbitals in the triangle. We show generally that the quasi-particle excitations from a local Fermi-liquid ground state acquire a channel symmetry at zero points of the two-terminal conductance, in the case the system has time-reversal and inversion symmetries. It causes the SU(4) behavior at low energies, while the orbital degeneracy in the triangle determines the high-energy behavior. At four-electron filling N_{tot} = 4.0, a local S=1 moment emerges at high temperatures due to a Nagaoka ferromagnetic mechanism. It is fully screened by the electrons from the two conducting channels via a two-stage Kondo effect, which is caused by a difference in the charge distribution in the even and odd orbitals.

18 pages, 16 figures, one new section VI is added

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• The Kondo crossover in shot noise of a single quantum dot with orbital degeneracy
• Realization of SU(N) Kondo effect in strong magnetic field
• Long-range Exchange Interaction in Triple Quantum Dots in the Kondo Regime
• Transport properties in a Non-Hermitian triple-quantum-dot structure
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• Reappearance of Kondo Effect in Serially Coupled Symmetric Triple Quantum Dots
• Dark states in spin-polarized transport through triple quantum dot molecules
• Magnetic Kondo regimes in a frustrated half-filled trimer
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• Local magnetic moments and electronic transport in closed loop quantum dot systems: a case of quadruple quantum dot ring at and away from equilibrium
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• Zero-field splitting of the Kondo resonance and quantum criticality in triple quantum dots
• Interaction induced local moments in parallel quantum dots within the functional renormalization group approach
• Quantum entanglement in a pure state of strongly correlated quantum impurity systems
• Unsupervised Learning of Effective Quantum Impurity Models
• Multistage Kondo effect in a multiterminal geometry: A modular quantum interferometer
• Kondo effect in Complex Quantum Dots in the presence of an oscillating and fluctuating gate signal
• Coherent time-dependent oscillations and temporal correlations in triangular triple quantum dots
• Kondo Screening of Local Moments in a Triangular Triple Quantum Dot Connected to Normal and Superconducting Leads