Coulomb frustrated Jahn-Teller phase transition in 2D

The properties of a system of charged particles on a 2D lattice, subject to an anisotropic Jahn-Teller-type interaction and 3D Coulomb repulsion are investigated. Without Coulomb repulsion the system displays a phase transition of first order with global phase separation at low temperature. At long distances Coulomb repulsion always dominates the short-range attraction leading to phase separation on a short scale. On the basis of Monte-Carlo simulation of microscopic lattice-gas model we have formulated an effective phenomenological model. In the limit of low density of polarons, phase separation takes place in the form of charged bubbles. In the limit of high density, charge segregation occurs in the form of charged bubbles and on charged domain walls.