Lin Xiao, Liu Zifei, Stauber Tobias, Gómez-Santos Guillermo, Gao Fei, Chen Hongsheng, Zhang Baile, Low Tony
Interdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Science and Technology Innovation Center, College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China.
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
Phys Rev Lett. 2020 Aug 14;125(7):077401. doi: 10.1103/PhysRevLett.125.077401.
van der Waals heterostructures of atomically thin layers with rotational misalignments, such as twisted bilayer graphene, feature interesting structural moiré superlattices. Because of the quantum coupling between the twisted atomic layers, light-matter interaction is inherently chiral; as such, they provide a promising platform for chiral plasmons in the extreme nanoscale. However, while the interlayer quantum coupling can be significant, its influence on chiral plasmons still remains elusive. Here we present the general solutions from full Maxwell equations of chiral plasmons in twisted atomic bilayers, with the consideration of interlayer quantum coupling. We find twisted atomic bilayers have a direct correspondence to the chiral metasurface, which simultaneously possesses chiral and magnetic surface conductivities, besides the common electric surface conductivity. In other words, the interlayer quantum coupling in twisted van der Waals heterostructures may facilitate the construction of various (e.g., bi-anisotropic) atomically-thin metasurfaces. Moreover, the chiral surface conductivity, determined by the interlayer quantum coupling, determines the existence of chiral plasmons and leads to a unique phase relationship (i.e., ±π/2 phase difference) between their transverse-electric (TE) and transverse-magnetic (TM) wave components. Importantly, such a unique phase relationship for chiral plasmons can be exploited to construct the missing longitudinal spin of plasmons, besides the common transverse spin of plasmons.
具有旋转错位的原子薄层范德华异质结构，如扭曲双层石墨烯，具有有趣的结构莫尔超晶格。由于扭曲原子层之间的量子耦合，光与物质的相互作用本质上是手性的；因此，它们为极端纳米尺度下的手性等离子体提供了一个有前景的平台。然而，尽管层间量子耦合可能很显著，但其对手性等离子体的影响仍然难以捉摸。在这里，我们给出了考虑层间量子耦合的扭曲原子双层中手性等离子体完整麦克斯韦方程的一般解。我们发现扭曲原子双层与手性超表面有直接对应关系，除了常见的电表面电导率外，它还同时具有手性和磁表面电导率。换句话说，扭曲范德华异质结构中的层间量子耦合可能有助于构建各种（例如，双各向异性）原子级薄的超表面。此外，由层间量子耦合决定的手性表面电导率决定了手性等离子体的存在，并导致其横向电（TE）和横向磁（TM）波分量之间存在独特的相位关系（即±π/2相位差）。重要的是，除了常见的等离子体横向自旋外，这种手性等离子体的独特相位关系可用于构建缺失的等离子体纵向自旋。
