Orbital ordering in undoped manganites via a generalized Peierls instability

TL;DR

This paper investigates the orbital ordering in undoped manganites, specifically LaMnO_3, using an extended Peierls instability framework to identify the dominant Jahn-Teller mode responsible for orbital order.

Contribution

It extends a Peierls instability framework to Jahn-Teller systems, revealing the Q2 mode as the key driver of orbital order in LaMnO_3 at weak coupling.

Findings

Q2 mode determines orbital order

Orbital ordering occurs at weak electron-phonon coupling

Extended Peierls framework applied to Jahn-Teller systems

Abstract

We study the ground state orbital ordering of $LaMnO_3$, at weak electron-phonon coupling, when the spin state is A-type antiferromagnet. We determine the orbital ordering by extending to our Jahn-Teller system a recently developed Peierls instability framework for the Holstein model [1]. By using two-dimensional dynamic response functions corresponding to a mixed Jahn-Teller mode, we establish that the $Q_2$ mode determines the orbital order.