Glasslike versus crystalline thermal conductivity in carrier-tuned Ba8Ga16X30 clathrates (X=Ge,Sn)
Glasslike versus crystalline thermal conductivity in carrier-tuned Ba8Ga16X30 clathrates (X=Ge,Sn)
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DOI：
10.1103/physrevb.74.125109
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发表时间：
2006-09-01
影响因子：
3.7
通讯作者：
Takabatake, T.
中科院分区：
文献类型：
--
作者：
Avila, M. A.;Suekuni, K.;Takabatake, T.
通过对载流子调谐的Ba 8 Ga 16 X 30（X=Ge，Sn）包合物的单晶X射线衍射、热导率kappa（T）和比热C-p（T）的研究，解决了目前在某些晶体材料中观察到的玻璃状热导率起源的争议。这些晶体显示出完全不同的低温kappa（T）行为，这取决于它们的电荷载流子是电子还是空穴，在前一种情况下显示出通常的结晶峰，而在后者中显示出异常的玻璃状平台。相比之下，C-p（T）高于4 K和一般的结构性质基本上是不敏感的载流子调谐。我们分析这些综合结果的框架内的隧道散射，共振散射和瑞利散射模型，并得出结论，从晶体到玻璃状kappa（T）的演变是伴随着隧道态的有效密度和共振散射水平的增加，而这些贡献都不能单独占观察到的变化在整个温度范围内。这表明，决定晶体或玻璃状行为的最相关因素是客体振动模式和具有不同电荷载流子的框架之间的耦合强度。
The present controversy over the origin of glasslike thermal conductivity observed in certain crystalline materials is addressed by studies on single-crystal x-ray diffraction, thermal conductivity kappa(T), and specific heat C-p(T) of carrier-tuned Ba8Ga16X30 (X=Ge,Sn) clathrates. These crystals show radically different low-temperature kappa(T) behaviors depending on whether their charge carriers are electrons or holes, displaying the usual crystalline peak in the former case and an anomalous glasslike plateau in the latter. In contrast, C-p(T) above 4 K and the general structural properties are essentially insensitive to carrier tuning. We analyze these combined results within the framework of tunneling scattering, resonant scattering, and Rayleigh scattering models, and conclude that the evolution from crystalline to glasslike kappa(T) is accompanied by an increase both in the effective density of tunneling states and in the resonant scattering level, while neither one of these contributions can solely account for the observed changes in the full temperature range. This suggests that the most relevant factor that determines crystalline or glasslike behavior is the coupling strength between the guest vibrational modes and the frameworks with different charge carriers.