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首页> 外文期刊>Physical review >Lattice dynamics in Bi_2Te_3 and Sb_2Te_3: Te and Sb density of phonon states
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Lattice dynamics in Bi_2Te_3 and Sb_2Te_3: Te and Sb density of phonon states

机译：Bi_2Te_3和Sb_2Te_3中的晶格动力学：声子态的Te和Sb密度

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摘要

The lattice dynamics in Bi_2Te_3 and Sb_2Te_3 were investigated both microscopically and macroscopically using ~(121) Sb and ~(125)Te nuclear inelastic scattering, x-ray diffraction, and heat capacity measurements. In combination with earlier inelastic neutron scattering data, the element-specific density of phonon states was obtained for both compounds and phonon polarization analysis was carried out for Bi_2Te_3. A prominent peak in the Te specific density of phonon states at 13 meV, that involves mainly in-plane vibrations, is mostly unaffected upon substitution of Sb with Bi revealing vibrations with essentially Te character. A significant softening is observed for the density of vibrational states of Bi with respect to Sb, consistently with the mass homology relation in the long-wavelength limit. In order to explain the energy mismatch in the optical phonon region, a ～20% force constant softening of the Sb-Te bond with respect to the Bi-Te bond is required. The reduced average speed of sound at 20 K in Bi_2Te_3, 1.75(1) km/s, compared to Sb_2Te_3, 1.85(4) km/s, is not only related to the larger mass density but also to a larger Debye level. The observed low lattice thermal conductivity at 295 K, 2.4 Wm~(-1)K~(-1) for Sb_2Te_3 and 1.6 Wm~(-1)K(-1) for Bi_2Te_3, cannot be explained by anharmonicity alone given the rather modest Grueneisen parameters, 1.7(1) for Sb_2Te_3 and 1.5(1) for Bi_2Te_3, without accounting for the reduced speed of sound and more importantly the low acoustic cutoff energy.
机译：使用〜（121）Sb和〜（125）Te核非弹性散射，X射线衍射和热容测量，从微观和宏观角度研究了Bi_2Te_3和Sb_2Te_3中的晶格动力学。结合较早的非弹性中子散射数据，获得了两种化合物的声子态元素比密度，并对Bi_2Te_3进行了声子极化分析。在13 meV时，声子态的Te比密度的一个突出峰主要涉及面内振动，在​​用Bi代替Sb时基本不受影响，从而揭示出本质上具有Te特性的振动。观察到Bi相对于Sb的振动态密度显着软化，这与长波长范围内的质量同源关系一致。为了解释光学声子区域中的能量失配，相对于Bi-Te键，需要Sb-Te键的〜20％力常数软化。与Sb_2Te_3、1.85（4）km / s相比，Bi_2Te_3在20 K下平均声音速度降低为1.75（1）km / s，这不仅与较大的质量密度有关，而且与较大的德拜级有关。在295 K，Sb_2Te_3的2.4 Wm〜（-1）K〜（-1）和Bi_2Te_3的1.6 Wm〜（-1）K（-1）处观察到的低晶格热导率不能单独用非谐性来解释适度的Grueneisen参数，Sb_2Te_3的参数为1.7（1），Bi_2Te_3的参数为1.5（1），但未考虑降低的声音速度以及更重要的是低的声截止能量。

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  • 来源
    《Physical review》 |2012年第22期|224301.1-224301.9|共9页
  • 作者

    D. Bessas; I. Sergueev; H.-C. Wille; J. Persson; D. Ebling; R. P. Hermann;

  • 作者单位

    Juelich Centre for Neutron Science JCNS and Peter Grtinberg Institut PGI, JARA-FIT, Forschungszentrum Juelich GmbH, D-52425 Juealich, Germany,Faculte des Sciences, Universite de Liege, B-4000 Liege, Belgium;

    Juelich Centre for Neutron Science JCNS and Peter Grtinberg Institut PGI, JARA-FIT, Forschungszentrum Juelich GmbH, D-52425 Juealich, Germany,European Synchrotron Radiation Facility, F-38043 Grenoble, France;

    Deutsches Elektronen-Synchrotron, D-22607 Hamburg, Germany;

    Juelich Centre for Neutron Science JCNS and Peter Grtinberg Institut PGI, JARA-FIT, Forschungszentrum Juelich GmbH, D-52425 Juealich, Germany;

    Fraunhofer Institut Physikalische Messtechnik, Heidenhofstrasse 8, D-79110 Freiburg, Germany,Fachhochschule Duesseldorf, Universitatsstrafie, D- 40225 Dusseldorf, Germany;

    Juelich Centre for Neutron Science JCNS and Peter Grtinberg Institut PGI, JARA-FIT, Forschungszentrum Juelich GmbH, D-52425 Juealich, Germany,Faculte des Sciences, Universite de Liege, B-4000 Liege, Belgium;

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  • 关键词

    moesbauer effect; other gamma-ray spectroscopy; thermoelectric and thermomagnetic effects;

    机译：莫斯鲍尔效应其他γ射线光谱学;热电和热磁效应;

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