Lattice Dynamics in a strongly dimerized low-dimensional model with orbital ordering

TL;DR

This paper investigates how spin, orbital, and lattice interactions influence phonon behavior in a one-dimensional model with orbital ordering, revealing the impact of Jahn-Teller distortions on phonon spectra.

Contribution

It introduces a detailed analysis of phonon renormalization due to orbital and magnetic excitations in a 1D Kugel-Khomskii model, highlighting the effects of different orbital orderings.

Findings

Orbiton shake-up processes depend on Jahn-Teller distortion type.

Phonon spectrum is significantly affected by orbital and magnetic excitations.

Results are relevant for interpreting optical spectra in low-dimensional transition metal compounds.

Abstract

We study the interplay of spin, orbital and lattice degrees of freedom in a one-dimensional Kugel-Khomskii model coupled to phonons. In the vicinity of the dimer point we analyze the excitation spectrum, mapping the spin and orbital degrees of freedom to bond operators. In particular we study the renormalization of the phonon propagator due to coupling to the orbital and magnetic excitations. Considering both, ferro- and antiferro-orbital ordering we will show that the appearance of orbiton shake-up processes in the phonon spectrum is sensitive to the type of Jahn-Teller distortion. The relevance of our results for optical spectroscopy on low dimensional transition metal compounds will be discussed.