Identification of coherent lattice modulations coupled to charge and orbital order in a manganite

TL;DR

This study uses femtosecond x-ray diffraction to explore atomic motions linked to charge and orbital order in a manganite, revealing a specific translational phonon mode involving Mn4+ and oxygen atoms.

Contribution

It provides detailed insight into the atomic motions associated with charge and orbital order in manganites using advanced femtosecond x-ray diffraction techniques.

Findings

Identification of a specific translational phonon mode involving Mn4+ and oxygen atoms.

Observation of the atomic response of superlattice reflections to optical phonon excitation.

Support for the coupling between lattice vibrations and charge/orbital order in manganites.

Abstract

We apply grazing-incidence femtosecond x-ray diffraction to investigate the details of the atomic motion connected with a displacively excited coherent optical phonon. We concentrate on the low frequency phonon associated with the charge and orbital order in the mixed valence manganite La0.25Pr0.375Ca0.375MnO3 for T < 210 K. We measure the response of three superlattice reflections that feature different sensitivities to the motion of the unit cell constituents. The results support the assignment to a translational mode of the Mn4+ atoms together with the oxygen atoms connecting adjacent Mn4+ sites.