2004/09/17 by Terutaka Goto, Terutaka Gotô, Yuichi Nemoto +5
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Center (category theory) #Chemistry #Condensed matter physics #Crystallography #Energy (signal processing) #Magnetic and transport properties of perovskites and related materials #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quantum tunnelling #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.70.184126
5 pages, 4 figures, to be published Phys. Rev. B
arxiv created 2004/09/17 · openalex publication_date 2004/11/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present tunneling and rattling motions of an off-center guest atom in a cage referring to a clathrate crystal La3Pd20Ge6. The elastic constant C44 of La3Pd20Ge6 shows a Debye-type dispersion of around 20\phantom\rule0.3em0exK obeying a relaxation time \ensuremathτ=\ensuremathτ0\phantom\rule0.2em0exexp(E∕kBT) with an attempt time of \ensuremathτ0=2.0\ifmmode×\else\texttimes\fi10^\ensuremath-12\phantom\rule0.3em0exs and an activation energy E=197\phantom\rule0.3em0exK. At low temperatures below 3\phantom\rule0.3em0exK down to 20\phantom\rule0.3em0exmK, the C44 shows a softening of C44=C440(T\ensuremath-TC0)∕(T\ensuremath-\ensuremathΘ) with TC0=\ensuremath-337.970\phantom\rule0.3em0exmK and \ensuremathΘ=\ensuremath-338.044\phantom\rule0.3em0exmK. These facts are attributed to two different types of off-center motions with \ensuremathΓ5 symmetry in the 4a-site cage of La3Pd20Ge6, a thermally activated rattling motion over the potential hill, and a tunneling motion through the potential hill at low temperatures.