Nanoscale Energy Confinement and Hybridization of Surface Plasmons Based on Skin Depth in Au/Ag Core-Shell Nanostructures

The electric field tends to become distributed within a conductor due to skin effect such that the field density is largest near the surface of the conductor and decreases with greater depths in the conductor. The electric field mainly distributes at the skin of the conductor, between the outer surface and a level called the skin depth. For a plasmonic nanosystem smaller than the skin depth, oscillations of the metal electrons will be driven by the optical electric field penetrating the entire system. This effect will induce confinement of optical energy inside the whole systems and influence the performance of surface plasmon. A theoretical model that a gold core is embedded within Ag nanoshell is constructed to simulate hybridization of surface plasmon and energy confinement in Au/Ag core/shell nanostructures based on the skin depth. Indeed, nanoshells in the core/shell system greatly influence the surface plasmon resonance, and the shell frequency is tuned efficiently through hybridization of surface plasmon. The plasmon resonances in core/shell particles can be understood in terms of hybridization between the plasmon modes of the surfaces and interfaces supported by cavity of the metallic shells. The hybridized plasmons induced by interaction of these plasmon modes can result in energy alteration over a wide range in wavelength. Combining with extinction spectra and field distributions, it can be seen that skin depth plays an important role in energy confinement and hybridization of surface plasmom.