Exceptional surface and bulk electronic structures in a topological insulator, Bi2Se3.
Exceptional surface and bulk electronic structures in a topological insulator, Bi2Se3.
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DOI：
10.1038/srep17351
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发表时间：
2015-12-08
影响因子：
4.6
通讯作者：
Maiti K
中科院分区：
文献类型：
--
作者：
Biswas D;Thakur S;Balakrishnan G;Maiti K
拓扑绝缘体的突出问题是拓扑有序表面态下的体金属性和远离费米能的狄拉克点的出现。人们正致力于通过暴露于外来材料来获得费米能级上的狄拉克点，以便这些材料可以用于技术并实现新的基础物理。具有讽刺意味的是，电子结构中的体金属性的结论基本上是基于角分辨光电子能谱，一种高度表面敏感的技术。在这里，我们采用了最先进的硬X射线光电子能谱与明智选择的实验几何形状来描绘的拓扑绝缘体和潜在的热电材料，Bi 2Se 3的体电子结构。结果显示出绝缘体电子结构的特征，其强度与半导体中的缺陷/空位诱导的掺杂态相似。芯能级光谱表现出与芯能级激发相关联的强等离子体激元峰，表明电子与集体激发耦合的特征，这是等离子体激元-声子耦合的可能情况。此外，一个新的损失功能出现在核心水平的光谱表明存在额外的集体激发系统。
The outstanding problem in topological insulators is the bulk metallicity underneath topologically ordered surface states and the appearance of Dirac point far away from the Fermi energy. Enormous efforts are being devoted to get the Dirac point at the Fermi level via exposure to foreign materials so that these materials can be used in technology and realize novel fundamental physics. Ironically, the conclusion of bulk metallicity in the electronic structure is essentially based on the angle resolved photoemission spectroscopy, a highly surface sensitive technique. Here, we employed state-of-the-art hard x-ray photoemission spectroscopy with judiciously chosen experiment geometry to delineate the bulk electronic structure of a topological insulator and a potential thermoelectric material, Bi2Se3. The results exhibit signature of insulating bulk electronic structure with tiny intensities at akin to defect/vacancy induced doped states in the semiconductors. The core level spectra exhibit intense plasmon peak associated to core level excitations manifesting the signature of coupling of electrons to the collective excitations, a possible case of plasmon-phonon coupling. In addition, a new loss feature appear in the core level spectra indicating presence of additional collective excitations in the system.