Universal slow plasmons and giant field enhancement in atomically thin quasi-two-dimensional metals
Universal slow plasmons and giant field enhancement in atomically thin quasi-two-dimensional metals
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DOI：
10.1038/s41467-020-14826-8
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发表时间：
2020-02-21
影响因子：
16.6
通讯作者：
Louie, Steven G.
中科院分区：
文献类型：
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作者：
da Jornada, Felipe H.;Xian, Lede;Louie, Steven G.
等离激元强烈依赖于维度：三维系统中的等离激元在波矢量 q=0 处以有限能量开始，而传统二维 (2D) 电子气中的等离激元则以 omega p 形式分散。然而，除了石墨烯之外，迄今为止，人们对真实的、原子级薄的准二维材料中的等离子体激元还没有很好的了解。在这里，我们表明，真正的准二维金属中的等离子体激元在性质上是不同的，对于典型实验感兴趣的波矢来说几乎是无色散的。这是由于连续平移对称性被破坏而导致带间筛选；因此，无色散等离子体激元是准二维金属中普遍存在的固有现象。此外，我们的从头计算表明，单层金属过渡金属二硫化物的等离子体激元是可调谐的、寿命长的、能够维持超过10(7)的场强增强，并且在实际空间中可局域化（类似于20nm内），在实际测量时间内几乎没有扩散。这为原子薄材料中的新型成像技术实时跟踪等离子体波包提供了可能性。
Plasmons depend strongly on dimensionality: while plasmons in three-dimensional systems start with finite energy at wavevector q=0, plasmons in traditional two-dimensional (2D) electron gas disperse as omega p. However, besides graphene, plasmons in real, atomically thin quasi-2D materials were heretofore not well understood. Here we show that the plasmons in real quasi-2D metals are qualitatively different, being virtually dispersionless for wavevectors of typical experimental interest. This stems from a broken continuous translational symmetry which leads to interband screening; so, dispersionless plasmons are a universal intrinsic phenomenon in quasi-2D metals. Moreover, our ab initio calculations reveal that plasmons of monolayer metallic transition metal dichalcogenides are tunable, long lived, able to sustain field intensity enhancement exceeding 10(7), and localizable in real space (within similar to 20nm) with little spreading over practical measurement time. This opens the possibility of tracking plasmon wave packets in real time for novel imaging techniques in atomically thin materials.