Temperature Dependent Phonon Spectra in Anharmonic Lattice with Cage-Like Structure

• Yamakage Ai

  Department of Physics, Tohoku University

• Kuramoto Yoshio

  Department of Physics, Tohoku University

抄録

Temperature dependent phonon spectra are derived for an anharmonic lattice model using the self-consistent harmonic approximation. The lattice consists of cage and guest ions with anharmonic guest–cage interaction. By using a quasi-isotropic harmonic interaction that leads to polarization-independent dynamical matrix, renormalized phonon spectra are derived explicitly for the whole Brillouin zone and for all branches. The largest softening with decreasing temperature occurs in an Einstein-like mode corresponding to oscillation of guest ions. Cage oscillations also show slight softening since the cage–cage force is partly mediated via guest ions. In the high-temperature region, frequency of the Einstein mode is proportional to T^1⁄4 in agreement with the behavior derived previously for an impurity model. As temperature decreases below the Einstein frequency, the renormalized phonon frequency decreases through an inflection point, and finally tends to T² variation. The behavior compares favorably with recent neutron scattering results in PrOs₄Sb₁₂. The temperature dependence of the sound velocity is also calculated, which agrees qualitatively with that observed in Sr₈Ga₁₆Ge₃₀.

収録刊行物

• Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｐｈｙｓｉｃａｌ　Ｓｏｃｉｅｔｙ　ｏｆ　Ｊａｐａｎ

  Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｐｈｙｓｉｃａｌ　Ｓｏｃｉｅｔｙ　ｏｆ　Ｊａｐａｎ 78 (6), 064602-064602, 2009

  一般社団法人 日本物理学会

キーワード

• anharmonic phonon
• skutterudite
• β-pyrochlore
• clathrate compounds
• self-consistent harmonic approximation

詳細情報

• CRID: 1390282679173185536
• NII論文ID: 130005437510
• NII論文ID: 10025961161
• NII論文ID: 210000107836
• NII書誌ID: AA00704814
• DOI: 10.1143/jpsj.78.064602
• BIBCODE: 2009JPSJ...78f4602Y
• ISSN: 13474073
• ISSN: 00319015
• NDL書誌ID: 10252494
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I10252494
• Web Site: https://journals.jps.jp/doi/pdf/10.1143/JPSJ.78.064602
• 本文言語コード: en
• データソース種別:
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