Mixed valence and superconductivity
Journal article, 2008

Mixed-valence (MV) systems are referred to here as MV-2 and MV-3 depending on whether two or three consecutive valence states are involved. MV-3 systems range from systems with Hubbard U≫0, corresponding to a single stable, intermediate valence state, and U≪0, corresponding to stable alternating valences differing by two units. Experiments using inelastic neutron scattering or inelastic X-ray scattering show softening of breathing phonon modes in MV systems compared with related systems with a single valence. It is hypothesized that softening is due to coupling between potential energy surfaces, corresponding to differing localizations of the electron. As predicted, softening is larger in the delocalized case. A mechanism for superconductivity is suggested. © 2007 The Royal Society.


Sven Larsson

Chalmers, Chemical and Biological Engineering, Physical Chemistry

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

1364-503X (ISSN) 1471-2962 (eISSN)

Vol. 366 1862 47-54

Subject Categories

Chemical Sciences



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