Optical conductivity from local anharmonic phonons

Hideki Matsumoto, Tatsuya Mori, Kei Iwamoto, Shohei Goshima, Syunsuke Kushibiki, Naoki Toyota

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Recently there has been paid much attention to phenomena caused by local anharmonic vibrations of the guest ions encapsulated in polyhedral cages of materials such as pyrochlore oxides, filled skutterdites, and clathrates. We theoretically investigate the optical conductivity solely due to these so-called rattling phonons in a one-dimensional anharmonic-potential model. The dipole interaction of the guest ions with electric fields induces excitations expressed as transitions among vibrational states with nonequally spaced energies, resulting in a natural line broadening and a shift of the peak frequency as anharmonic effects. In the case of a single-well potential, a softening of the peak frequency and an asymmetric narrowing of the line width with decreasing temperature are understood as a shift in the spectral weight to lower-level transitions. On the other hand, the case of a double-minima potential leads to a multisplitting of a spectral peak in the conductivity spectrum with decreasing temperature.

Original languageEnglish
Article number214306
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number21
Publication statusPublished - 2009 Jun 29
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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