Orbital ordering in undoped manganites using Jahn-Teller interaction

TL;DR

This paper investigates the orbital ordering in undoped manganites, specifically LaMnO3, by analyzing Jahn-Teller distortions and response functions, revealing that Q2 distortions dominate the orbital ordering at low temperatures.

Contribution

It provides a theoretical analysis of Jahn-Teller interactions and response functions to explain the orbital ordering mechanism in LaMnO3, highlighting the dominance of Q2 distortions.

Findings

Q2 response function diverges faster than Q3

Orbital ordering is dominated by Q2 distortions

Q2 excited state yields lower energy

Abstract

To understand the orbital ordering of $LaMnO_3$ in the ground state, we study it in the A-type spin antiferromagnetic state. We calculate the two-dimensional response functions associated with the Jahn-Teller $Q_2$ and $Q_3$ distortions and find that they diverge at the wavevector $\pi$,$\pi$). Furthermore, the $Q_2$ response function diverges faster which indicates that perhaps the ordering of the orbitals at low temperatures is dominated by the $Q_2$ distortion. We calculate the ground state energy for the cases when only one of the $Q_2$ and $Q_3$ modes is excited cooperatively and find that the $Q_2$ excited state yields lower energy.