Van der Waals heterostructures of atomically thin layers with rotational misalignments, such as twisted bilayer graphene, feature interesting structural moir superlattices. Due to 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., /2 phase difference) between their TE and 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.

中文翻译：

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具有扭曲原子双层的手性等离激元

具有旋转失准的原子薄层的Van der Waals异质结构，例如扭曲的双层石墨烯，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-质相互作用固有地是手性的。因此，它们为极端纳米级的手性等离激元提供了有希望的平台。然而，尽管层间量子耦合可能很重要，但它对手性等离子体激元的影响仍然难以捉摸。在这里，我们考虑了层间量子耦合，给出了扭曲原子双层中手性等离激元的完整麦克斯韦方程组的一般解。我们发现扭曲的原子双层与手性超表面具有直接对应关系，而手性超表面同时具有手性和磁性表面电导率，除了常见的表面导电性。换句话说，扭曲的范德华异质结构中的层间量子耦合可以促进各种（例如，双各向异性）原子薄的超表面的构造。此外，由层间量子耦合确定的手性表面电导率决定了手性等离子体激元的存在，并导致它们的TE和TM波分量之间具有独特的相位关系（即/ 2相差）。重要的是，除了等离激元的常见横向自旋之外，可以利用这种手性等离激元的独特的相位关系来构造缺失的等离激元的纵向自旋。双各向异性）原子薄的亚表面。此外，由层间量子耦合确定的手性表面电导率决定了手性等离子体激元的存在，并导致它们的TE和TM波分量之间具有独特的相位关系（即/ 2相差）。重要的是，除了等离激元的常见横向自旋之外，可以利用这种手性等离激元的独特的相位关系来构造缺失的等离激元的纵向自旋。双各向异性）原子薄的亚表面。此外，由层间量子耦合确定的手性表面电导率决定了手性等离子体激元的存在，并导致它们的TE和TM波分量之间具有独特的相位关系（即/ 2相差）。重要的是，除了等离激元的常见横向自旋之外，可以利用这种手性等离激元的独特的相位关系来构造缺失的等离激元的纵向自旋。