Charge Disproportionation, Mixed Valence, and Janus Effect in Multiorbital Systems: A Tale of Two Insulators

Multiorbital Hubbard models host strongly correlated "Hund's metals" even for interactions much stronger than the bandwidth. We characterize this interaction-resilient metal as a mixed-valence state. In particular, it can be pictured as a bridge between two strongly correlated insulat...

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Bibliographic Details
Published in:Physical review letters 2019-05, Vol.122 (18), p.186401-186401, Article 186401
Main Authors: Isidori, Aldo, Berović, Maja, Fanfarillo, Laura, De' Medici, Luca, Fabrizio, Michele, Capone, Massimo
Format: Article
Language:English
Subjects:
Chromates
Coupling
Disproportionation
Insulators
Physics
Valence
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Summary:Multiorbital Hubbard models host strongly correlated "Hund's metals" even for interactions much stronger than the bandwidth. We characterize this interaction-resilient metal as a mixed-valence state. In particular, it can be pictured as a bridge between two strongly correlated insulators: a high-spin Mott insulator and a charge-disproportionated insulator which is stabilized by a very large Hund's coupling. This picture is confirmed comparing models with negative and positive Hund's coupling for different fillings. Our results provide a characterization of the Hund's metal state and connect its presence with charge disproportionation, which has indeed been observed in chromates and proposed to play a role in iron-based superconductors.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.122.186401