Spin and orbital excitation spectrum in the Kugel-Khomskii model

TL;DR

This paper investigates the spin and orbital excitation spectrum in the three-dimensional Kugel-Khomskii model, revealing the stability of a specific ordered phase against quantum fluctuations.

Contribution

It provides a detailed analysis of quantum effects on orbital degeneracy and excitation damping in the Kugel-Khomskii model, focusing on a key point in the phase diagram.

Findings

Orbital degeneracy is lifted by quantum effects at a specific phase diagram point.

Spin and orbital excitations exhibit dispersion and damping influenced by their interaction.

The studied ordered phase remains stable against quantum fluctuations.

Abstract

We discuss spin and orbital ordering in the twofold orbital degenerate superexchange model in three dimensions relevant to perovskite transition metal oxides. We focus on the particular point on the classical phase diagram where orbital degeneracy is lifted by quantum effects exclusively. Dispersion and damping of the spin and orbital excitations are calculated at this point taking into account their mutual interaction. Interaction corrections to the mean-field order parameters are found to be small. We conclude that quasi-one-dimensional Neel spin order accompanied by the uniform d_{3z^2-r^2}-type orbital ordering is stable against quantum fluctuations.