このエントリーをはてなブックマークに追加
ID 30812
file
creator
Takasu, Yuichi
Avila, Marcos A.
NDC
Physics
abstract
To reveal dynamical property of a guest ion in type-I clathrate compound, n-and p-type clathrates Ba8Ga16Ge30 have been investigated by Raman scattering. It is found that the guest ion in a 6d-site cage (6d-cage) rotationally moves for both n-and p-type since the additional guest mode Eg(A) has been observed regardless of its carrier. The potential-energy difference between [100] and [110] directions in the 6d-cage is proportional to the off-center distance of the guest-ion position from the cage center and this off-center distance for p-type is much larger than that for n-type Ba8Ga16Ge30. In addition, the Raman intensity of the cage vibration at a 6c site for p-type is weaker than that for n-type. Thus, the amplitude of the vibration at the 6c site becomes small for p-type, and this small amplitude induces a large movable space for the guest ion, i.e., this vibrational amplitude of the 6c-site atom works as the barrier for the off-center position. For both systems, the guest ion in the 6d-cage shows an anharmonic vibration, judging from the anomalous energy decrease in the guest ion with decreasing temperature. The energy difference between T-2g and T-1u [T. Mori et al., Phys. Rev. B 79, 212301 (2009)] of the guest mode clearly supports the theoretical prediction of an interacting dipoles picture that explains the glasslike properties of the off-centered clathrate. It is concluded that the off-center rattling plays an important role to suppress a lattice thermal conductivity.
journal title
Physical Review B
volume
Volume 82
issue
Issue 13
start page
134320-1
end page
134320-7
date of issued
2010-10-05
publisher
American Physical Society
issn
1082-586X
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
Copyright (c) 2010 The American Physical Society
relation url
department
Graduate School of Integrated Arts and Sciences