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ID 19288
本文ファイル
著者
Takasu, Yuichi
Avila, Marcos A.
抄録(英)
Raman active phonons in the type-I clathrate compounds of X8 Ga16 Ge30 (X=Eu,Sr,Ba) have been fully assigned by the combination of polarized Raman scattering and first principles calculations. The dynamical motions of guest ions in the 6d -site cage have been clearly identified. The energy of the modes, related to a rattling motion, decreases with decreasing temperature. The energy-decrease at low temperatures is a common property for thermal rattling in X8 Ga16 Ge30. The anomalous decreases are originated from the quartic anharmonic potential, and its contribution has been experimentally determined. A mixed state between thermal rattling and quantum tunneling has been observed below 10 K. A soft mode due to the guest ion motion has been observed, but the transition due to this soft mode is somewhat different from the ordinary structural transition because of the shielding by carriers. In addition, it is found that the elastic dispersion of Sr8 Ga16 Ge30 is caused by the interference with the rattling motion of the guest ion in the cage, and that the rattling at the off-center location plays an important role to suppress a lattice thermal conductivity and to achieve the phonon-glass state in X8 Ga16 Ge30.
掲載誌名
Physical Review B - Condensed Matter and Materials Physics
74巻
17号
開始ページ
174303-1
終了ページ
174303-5
出版年月日
2006-11-22
出版者
American Physical Society
ISSN
1098-0121
NCID
出版者DOI
言語
英語
NII資源タイプ
学術雑誌論文
広大資料タイプ
学術雑誌論文
DCMIタイプ
text
フォーマット
application/pdf
著者版フラグ
publisher
権利情報
Copyright (c) 2006 The American Physical Society.
関連情報URL
部局名
総合科学研究科
先端物質科学研究科