1. Valence-skipping and negative-U in the d-band from repulsive local Coulomb interaction.
- Author
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Strand, Hugo U. R.
- Subjects
- *
VALENCE fluctuations , *COULOMB excitation , *DISPROPORTIONATION (Chemistry) , *ANISOTROPIC crystals , *BAND spectra , *TRANSITION metal compounds , *SUPERCONDUCTIVITY - Abstract
We show that repulsive local Coulomb interaction alone can drive valence-skipping charge disproportionation in the degenerate d-band, resulting in effective negative-U. This effect is shown to originate from anisotropic orbitalmultipole scattering, and it occurs only for d1, d4, d6, and d9 fillings (and their immediate surroundings). Explicit boundaries for valence-skipping are derived, and the paramagnetic phase diagram for d4 and d6 is calculated. We also establish that the valence-skipping metal is very different, in terms of its local valence distribution, compared to the atomiclike Hund's metal. These findings explain why transition-metal compounds with the aforementioned d-band fillings are more prone to valence-skipping charge order and anomalous superconductivity. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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