Twisting phonons in complex crystals with quasi-one-dimensional substructures
Twisting phonons in complex crystals with quasi-one-dimensional substructures
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DOI：
10.1038/ncomms7723
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发表时间：
2015-04-01
影响因子：
16.6
通讯作者：
Shi, Li
中科院分区：
文献类型：
--
作者：
Chen, Xi;Weathers, Annie;Shi, Li
许多晶体都含有准一维亚结构，这些亚结构具有独特的电子、自旋电子学、光学和热电性质。人们对影响这种复杂晶体性质的晶格动力学缺乏了解。在这里，我们采用非弹性中子散射测量和密度泛函理论计算表明，许多低能量的光学振动模式存在于更高的锰硅化物，这样的晶体的一个例子。这些光学模式，包括不寻常的低频扭曲运动的Si梯子内的Mn烟囱，散射声学声子提供了一个大的相空间。提出了一种混合声子和扩散模型来解释高锰硅化物的低和各向异性的热导率，并评估纳米结构作为进一步抑制热导率和提高热电能量转换效率的方法。这一发现提供了新的见解的结构与性能的关系，广泛的一类材料的准一维子结构的各种应用。
A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain the low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.