Temperature and magnetic field dependent Raman study of electron-phonon interactions in thin films of Bi2Se3 and Bi2Te3 nanoflakes
Temperature and magnetic field dependent Raman study of electron-phonon interactions in thin films of Bi2Se3 and Bi2Te3 nanoflakes
复制标题
DOI：
10.1103/physrevb.101.245431
复制
发表时间：
2020-06-22
影响因子：
3.7
通讯作者：
Ruebhausen, Michael
中科院分区：
文献类型：
--
作者：
Buchenau, Soeren;Scheitz, Sarah;Ruebhausen, Michael
利用温度和磁场相关的拉曼光谱研究了拓扑绝缘体Bi_2Se_3和Bi_2Te_3的二维纳米结构。我们的样品的表面贡献增加了通过使用薄膜的滴铸纳米片，目的是提高其拓扑性质。拉曼光谱提供了一种无接触的方法来研究低维下拓扑性质随温度和磁场的变化。温度依赖的拉曼研究揭示了非谐声子行为Bi2Te3表示在这种材料中的双声子弛豫机制。与此相反，Bi2Se3在低于120 K的温度下显示出明显偏离双声子非谐衰减模型，表现出硬化和加宽，特别是A（1g）（2）模式。同样，磁场依赖的自能效应只观察到的A（1g）（2）模式的Bi2Se3，显示出加宽和硬化随着磁场的增加。我们解释我们的结果在修正的声子自能Bi2Se3在温度低于120 K和磁场高于4 T由于电子空穴对激发与导电表面状态。随着磁场的增加，声子重整化被解释为在狄拉克锥，使声子耦合到变化的电极化率的间隙开口。
We have investigated two-dimensional nanostructures of the topological insulators Bi2Se3 and Bi2Te3 by means of temperature and magnetic field dependent Raman spectroscopy. The surface contribution of our samples was increased by using thin films of dropcasted nanoflakes with the aim of enhancing their topological properties. Raman spectroscopy provides a contact-free method to investigate the behavior of topological properties with temperature and magnetic fields at lower dimensions. The temperature dependent Raman study reveals anharmonic phonon behavior for Bi2Te3 indicative of a two-phonon relaxation mechanism in this material. Contrary to this, Bi2Se3 shows clear deviations from a two-phonon anharmonic decay model at temperatures below 120 K exhibiting a hardening and broadening, especially of the A(1g)(2) mode. Similarly, the magnetic field dependent self-energy effects are only observed for the A(1g)(2) mode of Bi2Se3, showing a broadening and hardening with increasing field. We interpret our results in terms of corrections to the phonon self-energy for Bi2Se3 at temperatures below 120 K and magnetic fields above 4 T due to electron-hole pair excitations associated with the conducting surface states. The phonon renormalization with increasing magnetic field is explained by a gap opening in the Dirac cone that enables phonon coupling to the changing electric susceptibility.