Song Chaoyu, Yuan Xiang, Huang Ce, Huang Shenyang, Xing Qiaoxia, Wang Chong, Zhang Cheng, Xie Yuangang, Lei Yuchen, Wang Fanjie, Mu Lei, Zhang Jiasheng, Xiu Faxian, Yan Hugen
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China.
Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, 200433, Shanghai, China.
Nat Commun. 2021 Jan 15;12(1):386. doi: 10.1038/s41467-020-20720-0.
Plasmons in two-dimensional (2D) materials beyond graphene have recently gained much attention. However, the experimental investigation is limited due to the lack of suitable materials. Here, we experimentally demonstrate localized plasmons in a correlated 2D charge-density-wave (CDW) material: 2H-TaSe. The plasmon resonance can cover a broad spectral range from the terahertz (40 μm) to the telecom (1.55 μm) region, which is further tunable by changing thickness and dielectric environments. The plasmon dispersion flattens at large wave vectors, resulted from the universal screening effect of interband transitions. More interestingly, anomalous temperature dependence of plasmon resonances associated with CDW excitations is observed. In the CDW phase, the plasmon peak close to the CDW excitation frequency becomes wider and asymmetric, mimicking two coupled oscillators. Our study not only reveals the universal role of the intrinsic screening on 2D plasmons, but also opens an avenue for tunable plasmons in 2D correlated materials.
除石墨烯之外的二维（2D）材料中的等离激元最近备受关注。然而，由于缺乏合适的材料，实验研究受到限制。在此，我们通过实验证明了在一种关联二维电荷密度波（CDW）材料2H-TaSe中存在局域等离激元。等离激元共振可覆盖从太赫兹（40μm）到电信波段（1.55μm）的宽广光谱范围，通过改变厚度和介电环境可进一步调节。由于带间跃迁的普遍屏蔽效应，等离激元色散在大波矢处变平。更有趣的是，观察到与CDW激发相关的等离激元共振存在异常的温度依赖性。在CDW相中，靠近CDW激发频率的等离激元峰变得更宽且不对称，类似于两个耦合振荡器。我们的研究不仅揭示了本征屏蔽对二维等离激元的普遍作用，还为二维关联材料中可调节等离激元开辟了一条途径。
