Vibronic polarons: comments on a model for the colossal field-resistance effects in manganites

TL;DR

This paper proposes a vibronic polaron model to explain colossal field-resistance effects in manganites, emphasizing the role of dipolar binding and external field coupling in charge ordering and phase transitions.

Contribution

It introduces a novel vibronic polaron framework accounting for various external fields influencing colossal resistance in manganites.

Findings

Charge-ordered phase formation via dipolar vibronic polarons

External fields induce polaron band widening and phase transitions

Model explains colossal effects beyond existing mechanisms

Abstract

In addition to mechanisms already proposed to account for the formation in manganites of a small-polaron superlattice above the Curie temperature Tc and to a metallic-like sea of large polarons below Tc, we now consider other observed colossal-resistance inducing fields, such as magnetic, electric, photon, or strain fields. We attribute the charge-ordered phase formation to the occurrence of strong dipolar binding of vibronic small polarons arising from the phonon coupling of highly polarizable two-level orbital systems. These species having associated inherent electric and magnetic off-center dipoles, they couple to the external fields leading to the observed colossal effects. The random phase appears due to polaron band widening in the external field.