Orbital Dynamics: The Origin of Anomalous Magnon Softening in Ferromagnetic Manganites

TL;DR

This paper investigates how charge, orbital, and lattice fluctuations influence magnon behavior in manganites, revealing that orbital fluctuations mainly cause the observed magnon softening at zone boundaries.

Contribution

It introduces a model coupling double-exchange interactions with Jahn-Teller phonons to explain magnon softening in ferromagnetic manganites.

Findings

Orbital fluctuations modulate ferromagnetic bonds.

Main origin of magnon softening identified as orbital fluctuations.

Model explains experimental magnon softening phenomena.

Abstract

We study the renormalization of magnons by charge and coupled orbital-lattice fluctuations in colossal magnetoresistance compounds. The model considered is an orbitally degenerate double-exchange system coupled to Jahn-Teller active phonons. The modulation of ferromagnetic bonds by low-energy orbital fluctuations is identified as the main origin of the unusual softening of the zone-boundary magnons observed experimentally in manganites.