The degenerate 3-band Hubbard model with "anti-Hund's rule" interactions; a model for AxC60

Abstract

We consider the orbitally degenerate 3-band Hubbard model with on-site interactions which favor low spin and low orbital angular momentum using standard second order perturbation theory in the large Hubbard-U limit. At even integer filling this model is a Mott insulator with a non-degenerate ground state that allows for a simple description of particle-hole excitations as well as gapped spin and orbital modes. We find that the Mott gap is generally indirect and that the single particle spectrum at low doping reappears close to even filling but rescaled by a factor 2/3 or 1/3. The model captures the basic phenomenology of the Mott insulating and metallic fullerides AxC60. This includes the existence of a smaller spin gap and larger charge gap at even integer filling, the fact that odd integer stoichiometries are generally metallic while even are insulating, as well as the rapid suppression of the density of states and superconducting transition temperatures with doping away from x=3.

arXiv commentRevised with additional references

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Cited by in corpus (5)

• Phases of a phenomenological model of twisted bilayer graphene
• Modeling the Unconventional Superconducting Properties of Expanded A${}_3$C${}_{60}$ Fullerides
• Paired chiral spin liquid with a Fermi surface in S=1 model on the triangular lattice
• QMC Calculation of the Electronic Binding Energy in a C60 Molecule
• Properties of the doped spin 3/2 Mott insulator near half filling