Relationship between orbital structure and lattice distortions: CE phase of manganites, revisited

TL;DR

This paper revisits the orbital structure and lattice distortions in the CE phase of manganites, emphasizing the importance of self-consistent analysis of electron-lattice interactions, kinetic energy, and crystal-field effects for accurate orbital identification.

Contribution

It demonstrates that traditional methods linking orbital occupation to ligand displacements can be misleading without self-consistent consideration of multiple interactions.

Findings

Incorrect orbital assignments can result from ignoring electron-lattice interactions.

In La$_{0.5}$Sr$_{1.5}$MnO$_4$, orbital ordering deviates from lattice distortion expectations.

Self-consistent analysis is essential for accurate orbital structure determination.

Abstract

Analyzing the orbital structure and lattice distortions in the CE phase of half-doped manganites, we demonstrate that the usual approach directly relating the orbital occupation of Jahn-Teller ions to the displacements of neighboring ligands may be misleading. For the correct identification of orbital structure, it is necessary to take self-consistently into account the electron-lattice interactions, kinetic energy of charge carriers, and crystal-field effects. In certain situations, e.g. in the CE phase of single-layered manganite La$_{0.5}$Sr$_{1.5}$MnO$_4$, the type of orbital ordering strongly deviates from that, which one would deduce from the local lattice distortions.