Manganites at Quarter Filling: Role of Jahn-Teller Interactions

TL;DR

This paper investigates the stabilization of the CE phase in half-doped manganites, emphasizing the critical role of cooperative Jahn-Teller interactions mediated by lattice distortions, using finite-temperature diagonalization.

Contribution

It demonstrates that cooperative Jahn-Teller interactions are essential for stabilizing the CE-type order in a realistic spin-orbital model of manganites.

Findings

CE phase appears in charge-ordered state with small antiferromagnetic interactions.

Cooperative Jahn-Teller interactions are key to stabilizing the CE-type spin and orbital order.

Topological phase factors and nearest neighbor JT coupling alone do not produce CE zigzag chains.

Abstract

We have analyzed different correlation functions in a realistic spin-orbital model for half-doped manganites. Using a finite-temperature diagonalization technique the CE phase was found in the charge-ordered phase in the case of small antiferromagnetic interactions between $t_{2g}$ electrons. It is shown that a key ingredient responsible for stabilization of the CE-type spin and orbital-ordered state is the cooperative Jahn-Teller (JT) interaction between next-nearest Mn$^{+3}$ neighbors mediated by the breathing mode distortion of Mn$^{+4}$ octahedra and displacements of Mn$^{+4}$ ions. The topological phase factor in the Mn-Mn hopping leading to gap formation in one-dimensional models for the CE phase as well as the nearest neighbor JT coupling are not able to produce the zigzag chains typical for the CE phase in our model.