Magnetic Kondo regimes in a frustrated half-filled trimer

We analyze theoretically the phase diagram of a triangular triple quantum dot with strong on-site repulsion coupled to ferromagnetic leads. This model includes the competition of magnetic ordering of local or itinerant magnetic moments, geometric frustration, and Kondo screening. We identify all the...

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Bibliographic Details
Published in:Physical review. B 2020-07, Vol.102 (4), p.1, Article 045144
Main Authors: Wójcik, Krzysztof P., Weymann, Ireneusz, Kroha, Johann
Format: Article
Language:English
Subjects:
Competition
Crossovers
Fermions
Ferromagnetism
Kondo effect
Lattices
Magnetic moments
Phase diagrams
Phases
Quantum dots
Trimers
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Summary:We analyze theoretically the phase diagram of a triangular triple quantum dot with strong on-site repulsion coupled to ferromagnetic leads. This model includes the competition of magnetic ordering of local or itinerant magnetic moments, geometric frustration, and Kondo screening. We identify all the phases resulting from this competition. We find that three Kondo phases-the conventional one, the two-stage underscreened one, and the one resulting from the ferromagnetic Kondo effect-can be realized at zero temperature, and all are very susceptible to the proximity of ferromagnetic leads. In particular, we find that the quantum dots are spin polarized in each of these phases. Further, we discuss the fate of the phases at nonzero temperatures, where a plethora of competing energy scales gives rise to a complex landscape of crossovers. Each Kondo regime splits into a pair of phases, one not magnetized and one comprising magnetically polarized quantum dots. We discuss our results in the context of heavy-fermion physics in frustrated Kondo lattices.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.102.045144