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Abstract:
We have analyzed the coexisting charge and orbital ordering in
half-doped manganites using a model which includes Coulomb and
Jahn-Teller orbital polarization interactions. Most
surprisingly, the gap in the optical conductivity is reduced by
both on-site and intersite Coulomb interactions, but increases
and explains the experimental results when the Jahn-Teller
terms with orbital polarization are considered. The origin of
this behavior is explained within a molecular model which
arises in the limit of extreme topological frustration, when
single electrons are confined to molecular units consisting of
three orbitals.
