Coherent optical and acoustic phonon generation correlated with the charge-ordering phase transition in La1-xCaxMnO3

D. Lim, V. K. Thorsmølle, R. D. Averitt, Q. X. Jia, K. H. Ahn, M. J. Graf, S. A. Trugman, A. J. Taylor

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37 Scopus citations

Abstract

We have observed coherent optical and acoustic phonon generation, which are strongly coupled to the charge-ordering (CO) transition in La1-xCaxMnO3 (x=0.5, 0.58) using femtosecond optical pump-probe spectroscopy. Coherent optical phonons, observed at low temperatures, disappear above the charge-ordering temperature TCO, while coherent acoustic phonons display the opposite behavior, disappearing gradually below TCO. Coherent optical phonons are generated by the displacive excitation mechanism where their coupling to the photoexcited charge carriers is enhanced by the structural change corresponding to the CO phase transition. The oscillation frequency for the coherent acoustic phonon depends on the probe wavelength, which is consistent with the propagating strain pulse mechanism. The dramatic change of lattice constants across the charge-ordering transition explains the overall temperature dependence of the coherent acoustic phonon amplitude.

Original languageEnglish (US)
Article number134403
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume71
Issue number13
DOIs
StatePublished - Dec 15 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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