Mott-Hubbard insulators for systems with orbital degeneracy

Abstract

We study how the electron hopping reduces the Mott-Hubbard band gap in the limit of a large Coulomb interaction U and as a function of the orbital degeneracy N. The results support the conclusion that the hopping contribution grows as roughly \sqrt{N}W, where W is the one-particle band width, but in certain models a crossover to a \sim NW behavior is found for a sufficiently large N.

7 pages, revtex, 6 figures more information at http://www.mpi-stuttgart.mpg.de/dokumente/andersen/fullerene/

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