论文标题
局部对称性对拓扑表面状态的晶格动力学的影响
Influence of local symmetry on lattice dynamics coupled to topological surface states
论文作者
论文摘要
我们研究了拓扑绝缘子BI2TE3中的耦合电子晶体动力学，并使用时间分辨光发射和时间分辨X射线衍射。可以通过光激发来启动连贯的声子，但是选择规则通常将这些模式限制为区域中心的波vectors和Raman-Active分支。我们发现，拓扑表面状态夫妇与其他模式，包括来自拉曼 - 和红外线的连续体散装散装模式，并且在存在时可能会产生表面占地模式的贡献。我们的计算表明，这种表面振动频谱自然出现是由于在表面上破裂的平移和反转对称性而无需表面局部定位的声子模式的分裂。该结果的一般性表明，连贯的声子光谱通过提供独特的指纹来识别更具争议性材料中的表面状态而有用。这些效果还可能扩大相位空间，以通过超快光激发来调整表面状态波形。
We investigate coupled electron-lattice dynamics in the topological insulator Bi2Te3 with time-resolved photoemission and time-resolved x-ray diffraction. It is well established that coherent phonons can be launched by optical excitation, but selection rules generally restrict these modes to zone-center wavevectors and Raman-active branches. We find that the topological surface state couples to additional modes, including a continuum of surface-projected bulk modes from both Raman- and infrared-branches, with possible contributions from surface-localized modes when they exist. Our calculations show that this surface vibrational spectrum occurs naturally as a consequence of the translational and inversion symmetries broken at the surface, without requiring the splitting-off of surface-localized phonon modes. The generality of this result suggests that coherent phonon spectra are useful by providing unique fingerprints for identifying surface states in more controversial materials. These effects may also expand the phase space for tailoring surface state wavefunctions via ultrafast optical excitation.
