Hu Li, Tian Xiaorui, Huang Yingzhou, Fang Liang, Fang Yurui
Soft Matter and Interdisciplinary Research Center, College of Physics, Chongqing University, Chongqing, 400044, P. R. China.
Nanoscale. 2016 Feb 14;8(6):3720-8. doi: 10.1039/c5nr08527f. Epub 2016 Jan 27.
Plasmonic chirality has drawn much attention because of tunable circular dichroism (CD) and the enhancement for chiral molecule signals. Although various mechanisms have been proposed to explain the plasmonic CD, a quantitative explanation like the ab initio mechanism for chiral molecules, is still unavailable. In this study, a mechanism similar to the mechanisms associated with chiral molecules was analyzed. The giant extrinsic circular dichroism of a plasmonic splitting rectangle ring was quantitatively investigated from a theoretical standpoint. The interplay of the electric and magnetic modes of the meta-structure is proposed to explain the giant CD. We analyzed the interplay using both an analytical coupled electric-magnetic dipole model and a finite element method model. The surface charge distributions showed that the circular current yielded by the splitting rectangle ring causes the ring to behave like a magneton at some resonant modes, which then interact with the electric modes, resulting in a mixing of the two types of modes. The strong interplay of the two mode types is primarily responsible for the giant CD. The analysis of the chiral near-field of the structure shows potential applications for chiral molecule sensing.
等离激元手性因其可调谐的圆二色性（CD）以及对手性分子信号的增强作用而备受关注。尽管已经提出了各种机制来解释等离激元CD，但类似于手性分子的从头算机制那样的定量解释仍然无法获得。在本研究中，分析了一种类似于与手性分子相关的机制。从理论角度对等离激元分裂矩形环的巨大外在圆二色性进行了定量研究。提出了超材料结构的电模式和磁模式之间的相互作用来解释这种巨大的CD。我们使用解析耦合电磁偶极子模型和有限元方法模型来分析这种相互作用。表面电荷分布表明，分裂矩形环产生的圆电流使环在某些共振模式下表现得像一个磁子，然后与电模式相互作用，导致两种模式混合。两种模式类型之间的强烈相互作用是产生巨大CD的主要原因。对该结构的手性近场分析表明其在手性分子传感方面具有潜在应用。
