Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites

TL;DR

This paper develops a detailed quantum mechanical model for manganites, revealing how lattice interactions influence spin and orbital correlations, and providing insights into complex orbital states relevant for colossal magnetoresistance.

Contribution

It introduces a realistic microscopic model including charge, spin, orbital, and lattice dynamics respecting SU(2) symmetry, and analyzes their interplay using exact diagonalisation.

Findings

Lattice interactions can suppress spin-orbital coupling.

Magnetic correlations are reflected in phonon dynamics.

Orbital correlations can form complex states.

Abstract

We derive a realistic microscopic model for doped colossal magnetoresistance manganites, which includes the dynamics of charge, spin, orbital and lattice degrees of freedom on a quantum mechanical level. The model respects the SU(2) spin symmetry and the full multiplet structure of the manganese ions within the cubic lattice. Concentrating on the hole doped domain ($0\le x\le 0.5$) we study the influence of the electron-lattice interaction on spin and orbital correlations by means of exact diagonalisation techniques. We find that the lattice can cause a considerable suppression of the coupling between spin and orbital degrees of freedom and show how changes in the magnetic correlations are reflected in dynamic phonon correlations. In addition, our calculation gives detailed insights into orbital correlations and demonstrates the possibility of complex orbital states.