Fig. 1. Tunable plasmon resonance in gated plasmon ribbon array^[7]: (a) Schematic of the device (upper panel) and AFM image of a typical ribbon array (lower panel); (b) gate dependent plasmon resonance with light polarization perpendicular to the ribbon array. Inset shows the spectra with parallel light polarization; (c) normalized plasmon frequency as a function of Fermi energy and carrier density for different ribbon width. 石墨烯等离激元的电学调控^[7] 　(a)器件示意图(上图)和石墨烯光栅结构AFM轮廓图(下图); (b)石墨烯光栅在不同门电压下的透射光谱图. 主图为入射光偏振垂直于光栅方向, 插图为偏振平行于光栅方向; (c)不同宽度光栅的等离激元频率随载流子浓度(费米面能量)的依赖关系

Fig. 2. Band structures for different types of topological materials: (a) Topological insulator [from Wikipedia]; (b) topological semimetals^[37]. 不同拓扑材料的能带示意图　(a)拓扑绝缘体(来自维基百科); (b)拓扑半金属(来自文献[37])

Fig. 3. Hybrid plasmon modes in topological insulator thin slabs^[43]: (a) Schematic of optical mode and acoustic mode; (b) plasmon dispersion in 6 nm topological insulator film. 拓扑绝缘体薄膜上下表面狄拉克等离激元的混合模式^[43] 　(a)拓扑绝缘体薄膜光学支和声学支等离激元振动示意图; (b) 6 nm厚拓扑绝缘体薄膜的两支(同相位和反相位)等离激元模式色散曲线

Fig. 4. Far filed spectroscopic study of the plasmon modes in topological insulator films: (a) Extinction spectra of plasmon resonance modes in topological insulator ribbon arrays with different width; (b) plasmon dispersion extracted from Fig. (a). Fig. (a) and Fig. (b) from Ref. [46]; (c) magnetoplasmon mode and cyclotron resonance in topological insulator ribbon array as a function of external magnetic field^[47]; (d) plasmon dispersion in topological insulator microring array^[48]; (e) plasmon resonance modes of topological insulator ribbon array from visible to ultraviolet frequency range^[49]; (f) plasmon dispersion as a function of film thickness in topological insulator ribbon arrays^[50]. 拓扑绝缘体等离激元的远红外和可见光远场光谱研究　(a)不同光栅宽度下拓扑绝缘体薄膜等离激元共振模式远红外吸收谱^[46]; (b)由(a)中实验得到的等离激元色散关系^[46]. 虚线和点线分别为考虑表面态电子和体载流子后计算的等离激元色散; (c)外加垂直于面的磁场后, 拓扑绝缘体薄膜光栅结构中磁性等离激元和回旋共振模式随磁场的变化关系^[47]; (d)圆环阵列结构下, 拓扑绝缘体薄膜等离激元色散关系^[48]; (e)可见到紫外波段拓扑绝缘体等离激元共振模式^[49]; (f)拓扑绝缘体薄膜光栅结构中等离激元共振模式随着薄膜厚度的依赖关系^[50]

Fig. 5. EELS study of plasmon modes in topological insulator: (a) EELS spectra at different spots from the edge (upper panel). Calculated permittivity from the black line (lower panel)^[53]; (b) plasmon dispersion derived from the EELS spectra with high energy resolution^[54]; (c) unusual acoustic plasmon modes with linear dispersion measured with high energy resolution EELS^[57]. 拓扑绝缘体等离激元电子能量损失谱研究　(a)距离晶体边界不同位置处的能量损失谱(上图)和由上图黑线导出的介电常数(下图)^[53]; (b)高能量分辨EELS测量到的拓扑绝缘体等离激元色散模式^[54]; (c)高能量分辨EELS测量到的具有线性色散的声学支等离激元模式^[57]

Fig. 6. Experiments of plasmons in topological semimetals: (a) Bulk plasmon dispersion in PtTe₂ measured by EELS^[60]; (b) energy loss spectra of plasmon modes in NbAs and TaAs measured by EELS^[61]; (c) transmission spectra of plasmon modes of Cd₂As₃ in THz range^[62]. (d) and (e) temperature dependence of the anisotropic bulk plasmon and effective mass ratio in WTe₂^[63]. 拓扑半金属等离激元研究 (a)利用EELS测量PtTe₂中体等离激元色散模式^[60]; (b)超高分辨EELS下测到的NbAs和TaAs表面等离激元模式^[61]; (c)太赫兹波段Cd₂As₃薄膜的光栅结构中等离激元的远场透射谱^[62]; (d)和(e)由WTe₂体材料单晶的反射谱得到的各向异性体等离激元频率(d)和有效质量比(e)随温度的变化^[63]

Fig. 7. Synthesis of topological material films with large area and high quality by CVD method: (a) to (c) CVD growth of large area single crystal films of WTe₂ and MoTe₂^[78]; (d) and (e) large area MoTe₂ film grown from Mo^[79]. 大面积高质量拓扑材料薄膜CVD生长　(a)—(c) CVD方法生长大面积WTe₂和MoTe₂单晶薄膜^[78]; (d), (e)利用Te化金属薄膜的方法生长大面积多晶MoTe₂薄膜^[79]