Strong circular dichroism of core-shell magnetoplasmonic nanoparticles

Abstract

Composite magnetoplasmonic nanoparticles with a core-shell morphology exhibit intriguing optical properties and offer impressive opportunities for tailoring in a controllable manner the light-matter interaction at subwavelength dimensions. These properties are usually analyzed in the framework of the quasi-static approximation, which, however, is often inadequate; thus, a full electrodynamic treatment is required. In this respect, we developed a rigorous method for an accurate description of electromagnetic scattering by a gyrotropic sphere coated with a nongyrotropic concentric spherical shell, based on the full multipole expansion of the wave field. The method was applied to specific examples of core-shell cobalt-silver spherical nanoparticles, where the occurrence of strong circular dichroism induced by magnetoplasmonic interaction, which largely exceeds that of homogeneous noble metal nanoparticles in an external magnetic field, was found. Our results were also explained by reference to the quasi-static approximation, which, though it reproduces the main features of the absorption spectra, strongly overestimates circular dichroism in the cases we studied.

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“…2.4. T-matrix theory and computations for anisotropic, chiral, gyrotropic, magnetic, and charged scatterers [31,37,38,60,80,107,123,124,185,191,192,215].…”

Hybrid Magneto-Plasmonic Nanoparticles in Biomedicine: Fundamentals, Synthesis and Applications

“…This force confines or expands the circular trajectories depending on their helicity and shifts the LSPR to lower and higher frequencies of the spectrum, respectively. This effect can be enhanced using composite nanomaterials [32].…”

Metal-coated magnetic nanoparticles in an optically active medium: A nonreciprocal metamaterial

“…In a dielectric, in general bianisotropic, medium, along any direction, the dispersion relation has two extended branches corresponding to the two linearly independent transverse polarization eigenmodes of waves propagating in this medium. However, for the structure under consideration, the effectivemedium approximation describes, also, localized dipole plasmons at the two metal-dielectric interfaces [32,33] and, thus, in addition to the extended dispersion curves, six narrow bands (three originating from the cavitylike and three from the particlelike collective dipole plasmon modes) are obtained as well. In general, when two bands of the same symmetry cross each other, level repulsion leads to the opening of a frequency gap about the crossing point.…”