Plasmonic resonances of nanoparticles have drawn lots of attention due to their interesting and useful properties such as strong field enhancements. The self-consistent hydrodynamics model has the advantage that it can incorporate the quantum effect of the electron gas into classical electrodynamics in a consistent way. We use the method to study the plasmonic response of polygonal rods under the influence of an external electromagnetic wave, and we pay particular attention to the size and shape of the particle and the effect of charging. We find that the particles support edge modes, face modes, and hybrid modes. The charges induced by the external field in the edge (face) modes mainly localize at the edges (faces), while the induced charges in the hybrid modes are distributed nearly evenly in both the edges and faces. The edge modes are less sensitive to particle size than the face modes but are sensitive to the corner angles of the edges. When the number of sides of regular polygons increases, the edge and face modes gradually change into the classical dipole plasmonic mode of a cylinder. The hybrid modes are found to be the precursor of the Bennett mode, which cannot be found in classical electrodynamics.

中文翻译：

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用量子流体动力学方法计算的多边形棒的等离子模式

纳米粒子的等离子体共振由于其有趣和有用的特性（例如强场增强）而引起了很多关注。自洽流体力学模型的优势在于，它可以以一致的方式将电子气的量子效应纳入经典的电动力学中。我们使用该方法来研究多边形棒在外部电磁波的影响下的等离子体响应，并特别注意粒子的大小和形状以及带电效应。我们发现粒子支持边缘模式，面部模式和混合模式。边缘（面部）模式中的外部电场感应的电荷主要位于边缘（面部），而混合模式中的感应电荷几乎均匀地分布在边缘和面部。边缘模式对粒子大小的敏感性不如面部模式，但对边缘的转角敏感。当规则多边形的边数增加时，边模和面模逐渐变为圆柱体的经典偶极等离子体模式。混合模式被发现是贝内特模式的前身，这在经典的电动力学中是找不到的。