We analyze the electromagnetic field near a plane interface between a conductive and a dielectric media, under conditions supporting surface plasmon-polariton (SPP) propagation. The conductive medium is described by the hydrodynamic electron-gas model that enables a consistent analysis of the field-induced variations of the electron density and velocity at the interface and its nearest vicinity. The distributions of electromagnetic dynamical characteristics: energy, energy flow, spin and momentum are calculated analytically and illustrated numerically, employing silver-vacuum interface as an example. A set of the “field” and material contributions to the energy, spin and momentum are explicitly identified and classified with respect to their physical origins and properties, and the orbital (canonical) and spin (Belinfante) momentum constituents are separately examined. In this context, a procedure for the spin-orbital momentum decomposition in the presence of free charges is proposed and substantiated. The microscopic results agree with the known phenomenological data but additionally show specific nanoscale structures in the near-interface behavior of the SPP energy and momentum, which can be deliberately created, controlled and used in nanotechnology applications.

中文翻译：

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表面等离子体激元波中能量、动量和自旋分布的显微分析

我们在支持表面等离子体激元 (SPP) 传播的条件下分析了导电介质和电介质之间的平面界面附近的电磁场。导电介质由流体动力学电子-气模型描述，该模型能够对界面及其最近附近的电子密度和速度的场致变化进行一致的分析。以银-真空界面为例，对电磁动力学特性的分布：能量、能流、自旋和动量进行了解析计算和数值说明。一组对能量、自旋和动量的“场”和材料贡献根据它们的物理起源和性质被明确识别和分类，轨道（规范）和自旋（Belinfante）动量成分分别进行了检查。在这种情况下，提出并证实了存在自由电荷时的自旋轨道动量分解过程。微观结果与已知的现象学数据一致，但在 SPP 能量和动量的近界面行为中还显示了特定的纳米级结构，可以有意地创建、控制和用于纳米技术应用。