title: Quantitatively analyzing the mechanism of giant circular dichroism in extrinsic plasmonic chiral nanostructures by tracking the interplay of electric and magnetic dipoles.
abstract: 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.
authors.affiliation: Soft Matter and Interdisciplinary Research Center, College of Physics, Chongqing University, Chongqing, 400044, P. R. China.
authors.forename: Li
authors.initials: L
authors.lastname: Hu
authors.forename: Xiaorui
authors.initials: X
authors.lastname: Tian
authors.forename: Yingzhou
authors.initials: Y
authors.lastname: Huang
authors.forename: Liang
authors.initials: L
authors.lastname: Fang
authors.forename: Yurui
authors.initials: Y
authors.lastname: Fang