Kondo effects in a triangular triple quantum dot: NRG study in the whole region of the electron filling - Condensed Matter > Mesoscale and Nanoscale PhysicsReport as inadecuate




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Abstract: We study the low-energy properties of a triangular triple quantum dotconnected to two non-interacting leads in a wide parameter range, using thenumerical renormalization group NRG. Various kinds of Kondo effects takeplace in this system depending on the electron filling N {tot}, or the levelposition $\epsilon d$ of the triple dot. The SU4 Kondo behavior is seen inthe half-filled case N {tot} = 3.0 at the dip of the series conductance, and itcauses a charge redistribution between the even and odd orbitals in thetriangle. We show generally that the quasi-particle excitations from a localFermi-liquid ground state acquire a channel symmetry at zero points of thetwo-terminal conductance, in the case the system has time-reversal andinversion symmetries. It causes the SU4 behavior at low energies, while theorbital degeneracy in the triangle determines the high-energy behavior. Atfour-electron filling N {tot} = 4.0, a local S=1 moment emerges at hightemperatures due to a Nagaoka ferromagnetic mechanism. It is fully screened bythe 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 oddorbitals.



Author: Takahide Numata, Yunori Nisikawa, Akira Oguri, Alex C. Hewson

Source: https://arxiv.org/







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