Inhomogeneous States in Strongly Correlated Electron Systems with Orbital Degrees of Freedom

Abstract

We study a strongly correlated electron system with charge carriers characterized by different values of orbital quantum number. It is shown that such a system exhibits a tendency to phase separation owing to a competition between the charge localization in the orbitally ordered state and metallicity. The effect of orbital ordering on the phase separation is studied employing a minimal model including itinerant charge carriers at the orbitally ordered background. It is shown that at low doping, the phase separation may appear in systems with orbital degeneracy even without taking into account the magnetic structure. We considered this effect using two versions of the model. In the first one, we assumed that in the absence of doping, the orbital structure results from the interaction of core electrons with the lattice. Electrons appearing due to doping move in this background. In an alternative model, the same electrons take part in the formation of both band structure and orbital ordering.