Doped orbitally-ordered systems: another case of phase separation

TL;DR

This paper proposes a mechanism for electronic phase separation in orbitally-ordered systems, highlighting how doping-induced charge delocalization and lattice distortions lead to nanoscale inhomogeneities without magnetic order.

Contribution

It introduces a simple model demonstrating phase separation driven by charge delocalization and orbital ordering, independent of magnetic interactions.

Findings

Charge carriers promote nanoscale inhomogeneities.

Orbital inhomogeneities vary in shape and size.

Mechanism is similar to double exchange but without magnetic order.

Abstract

A possible mechanism of electronic phase separation in the systems with orbital ordering is analyzed. We suggest a simple model taking into account an interplay between the delocalization of charge carriers introduced by doping and the cooperative ordering of local lattice distortions. The proposed mechanism is quite similar to the double exchange usually invoked for interpretation of phase separation in doped magnetic oxides like manganites, but can be efficient even in the absence of any magnetic ordering. It is demonstrated that the delocalized charge carriers favor the formation of nanoscale inhomogeneities with the orbital structure different from that in the undoped material. The directional character of orbitals leads to inhomogeneities of different shapes and sizes.