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Nanoscale surface dynamics of Bi2Te3(111): observation of a prominent surface acoustic wave and the role of van der Waals interactions
Nanoscale ( IF 6.7 ) Pub Date : 2018-07-16 00:00:00 , DOI: 10.1039/c8nr03102a
Anton Tamtögl 1, 2, 3, 4, 5 , Davide Campi 6, 7, 8, 9 , Martin Bremholm 10, 11, 12, 13, 14 , Ellen M. J. Hedegaard 10, 11, 12, 13, 14 , Bo B. Iversen 10, 11, 12, 13, 14 , Marco Bianchi 12, 13, 14, 15, 16 , Philip Hofmann 12, 13, 14, 15, 16 , Nicola Marzari 6, 7, 8, 9 , Giorgio Benedek 17, 18, 19, 20, 21 , John Ellis 1, 2, 3 , William Allison 1, 2, 3
Affiliation  

We present a combined experimental and theoretical study of the surface vibrational modes of the topological insulator Bi2Te3. Using high-resolution helium-3 spin-echo spectroscopy we are able to resolve the acoustic phonon modes of Bi2Te3(111). The low energy region of the lattice vibrations is mainly dominated by the Rayleigh mode which has been claimed to be absent in previous experimental studies. The appearance of the Rayleigh mode is consistent with previous bulk lattice dynamics studies as well as theoretical predictions of the surface phonon modes. Density functional perturbation theory calculations including van der Waals corrections are in excellent agreement with the experimental data. Comparison of the experimental results with theoretically obtained values for films with a thickness of several layers further demonstrate, that for an accurate theoretical description of three-dimensional topological insulators with their layered structure the inclusion of van der Waals corrections is essential. The presence of a prominent surface acoustic wave and the contribution of van der Waals bonding to the lattice dynamics may hold important implications for the thermoelectric properties of thin-film and nanoscale devices.

中文翻译:

Bi 2 Te 3(111)的纳米尺度表面动力学:观察到明显的声表面波以及范德华相互作用的作用

我们目前对拓扑绝缘子Bi 2 Te 3的表面振动模式进行了组合的实验和理论研究。使用高分辨率氦3自旋回波光谱仪,我们能够解析Bi 2 Te 3的声子声子模(111)。晶格振动的低能量区域主要由瑞利模式控制,该方法在先前的实验研究中被认为是不存在的。瑞利模式的出现与先前的体晶格动力学研究以及表面声子模式的理论预测是一致的。包括范德华校正在内的密度泛函扰动理论计算与实验数据非常吻合。将实验结果与具有几层厚度的薄膜的理论获得的值进行比较,进一步证明,对于具有分层结构的三维拓扑绝缘体的准确理论描述,必须包括范德华校正。
更新日期:2018-07-16
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