Jahn-Teller Effect and Superexchange in Half-Doped Manganites

TL;DR

This paper explores how superexchange interactions influence the stability of the CE phase in half-doped manganites, emphasizing the importance of interaction strength beyond spectroscopic estimates.

Contribution

It introduces a microscopic model including Coulomb, Jahn-Teller, and superexchange interactions to analyze phase stability in manganites.

Findings

Superexchange interactions can stabilize the CE phase.

Stability requires superexchange stronger than spectroscopic estimates.

Phase diagram analyzed at zero temperature.

Abstract

We investigate the stability of the charge exchange (CE) phase within a microscopic model which describes a single plane as in La$_{0.5}$Sr$_{1.5}$MnO$_4$. The model includes Coulomb interactions (on-site and intersite), the Jahn-Teller term and the superexchange interactions due to $e_g$ and $t_{2g}$ electrons. By investigating the phase diagram at T=0 in mean-field approximation we conclude that the superexchange interactions can stabilize the CE phase, but only if they are stronger than estimated from spectroscopy.