Optical conductivity of rattling phonons in type-I clathrates Ba 8Ga16Ge30 and Ba8Ga 16Sn30

K. Iwamoto, T. Mori, S. Kushibiki, H. Honda, H. Matsumoto, K. Suekuni, M. A. Avila, T. Takabatake, N. Toyota

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

We review our dynamical property measurements of rattling phonons in type-I clathrate compounds, the quasi-on-center Ba8Ga16Ge 30 (BGG) and off-center Ba8Ga16Sn30 (BGS), using a terahertz time-domain spectrometer. The lowest-lying vibrational modes of rattling Ba ions in the oversized cage show anomalous temperature dependence in their spectra. For BGG, the temperature dependence is mostly consistent with a local anharmonic potential approximation that predicts softening towards low temperature. On the other hand, for BGS, a single broad peak of off-center rattling phonons splits into two subpeaks below 120 K, and, with further lowering temperature, the spectra show anomalous broadening. While the splitting can be understood by the double well potential, the linewidth broadening must be attributed to some relevant interactions with such excitations as acoustic phonons and doped carriers.

Original languageEnglish
Title of host publicationMaterials Integration
PublisherTrans Tech Publications Ltd
Pages341-346
Number of pages6
ISBN (Print)9783037853764
DOIs
Publication statusPublished - 2012 Jan 1
EventInt. Symposium of GCOE: Materials Integration, in Conjunction with the 2nd Int. Symposium on Advanced Synthesis and Processing Technology for Materials, ASPT 2011 and the 8th Materials Science School for Young Scientists, KINKEN-WAKATE 2011 - Sendai, Japan
Duration: 2011 Dec 12011 Dec 2

Publication series

NameKey Engineering Materials
Volume508
ISSN (Print)1013-9826
ISSN (Electronic)1662-9795

Other

OtherInt. Symposium of GCOE: Materials Integration, in Conjunction with the 2nd Int. Symposium on Advanced Synthesis and Processing Technology for Materials, ASPT 2011 and the 8th Materials Science School for Young Scientists, KINKEN-WAKATE 2011
CountryJapan
CitySendai
Period11/12/111/12/2

Keywords

  • Clathrates
  • Optical conductivity
  • Rattling phonons
  • Terahertz time-domain spectroscopy
  • Thermoelectrics

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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  • Cite this

    Iwamoto, K., Mori, T., Kushibiki, S., Honda, H., Matsumoto, H., Suekuni, K., Avila, M. A., Takabatake, T., & Toyota, N. (2012). Optical conductivity of rattling phonons in type-I clathrates Ba 8Ga16Ge30 and Ba8Ga 16Sn30. In Materials Integration (pp. 341-346). (Key Engineering Materials; Vol. 508). Trans Tech Publications Ltd. https://doi.org/10.4028/www.scientific.net/KEM.508.341