Charge melting and polaron collapse in $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$

TL;DR

This study uses X-ray and neutron scattering to show how polarons in a manganite compound form short-range correlations that vanish at the ferromagnetic transition, shedding light on their role in colossal magnetoresistance.

Contribution

It provides direct experimental evidence of polaron behavior and their abrupt disappearance at the ferromagnetic transition in a colossal magnetoresistive oxide.

Findings

Polarons exhibit short-range correlations that grow with decreasing temperature.

Polaron correlations disappear abruptly at the ferromagnetic transition.

Charge delocalization occurs with the collapse of polaron scattering.

Abstract

X-ray and neutron scattering measurements directly demonstrate the existence of polarons in the paramagnetic phase of optimally-doped colossal magnetoresistive oxides. The polarons exhibit short-range correlations that grow with decreasing temperature, but disappear abruptly at the ferromagnetic transition because of the sudden charge delocalization. The "melting" of the charge ordering as we cool through $T_C$ occurs with the collapse of the quasi-static polaron scattering, and provides important new insights into the relation of polarons to colossal magnetoresistance.