  Based on the analysis of a two-orbital Hubbard model within a mean-field
approach, we propose a mechanism for an orbital selective phase transition
(OSPT) where coexistence of localized and itinerant electrons can be realized.
We show that this OSPT exists both at and near half filling even in the absence
of crystal field splittings or when bandwidths, orbital degeneracies and
magnetic states are equal for both orbitals provided the orbitals have
different band dispersions. Such conditions should be generally satisfied in
many materials. We find that this OSPT is not sensitive to the strength of
Hund's rule coupling and that heavy doping favors the collinear
antiferromagnetic state over the OSPT. We discuss our results in relation to
the iron pnictides.
