The Charge Ordered State from Weak to Strong Coupling

TL;DR

This paper uses Dynamical Mean Field Theory to study charge ordering in materials, revealing how polarons influence the charge ordered state and its optical properties across different coupling regimes.

Contribution

It introduces a detailed analysis of charge ordering from weak to strong coupling, emphasizing the role of polarons and lattice polarization in this process.

Findings

Polarons are crucial in both normal and charge ordered states.

Charge order at intermediate and strong coupling involves thermally activated defects.

The properties of the charge ordered state explain low-frequency optical conductivity in Ni perovskites.

Abstract

We apply the Dynamical Mean Field Theory to the problem of charge ordering. In the normal state as well as in the Charge Ordered (CO) state the existence of polarons, i.e. electrons strongly coupled to local lattice deformation, is associated to the qualitative properties of the Lattice Polarization Distribution Function (LPDF). At intermediate and strong coupling a CO state characterized by a certain amount of thermally activated defects arise from the spatial ordering of preexisting randomly distributed polarons. Properties of this particular CO state gives a qualitative understanding of the low frequency behavior of optical conductivity of $Ni$ perovskites.