Dispersion of orbital excitations in 2D quantum antiferromagnets

TL;DR

This paper investigates the behavior of orbital excitations in two-dimensional quantum antiferromagnets, revealing their coupling to magnons and the resulting dispersion relation, which differs from mean-field predictions.

Contribution

It maps the orbital excitation problem onto a hole in a 2D antiferromagnet, demonstrating the importance of magnetic dressing for orbital mobility.

Findings

Orbital excitations are coupled to magnons.

Dispersion reflects the two-site unit cell of the antiferromagnetic background.

Mean-field and linear orbital-wave theories do not capture the true dispersion.

Abstract

We map the problem of the orbital excitation (orbiton) in a 2D antiferromagnetic and ferroorbital ground state onto a problem of a hole in 2D antiferromagnet. The orbiton turns out to be coupled to magnons and can only be mobile on a strongly renormalized scale by dressing with magnetic excitations. We show that this leads to a dispersion relation reflecting the two-site unit cell of the antiferromagnetic background, in contrast to the predictions based on a mean-field approximation and linear orbital-wave theory.