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@article{Schnitzer:2015:10.1103/PhysRevB.92.235428,
author = {Schnitzer, O},
doi = {10.1103/PhysRevB.92.235428},
journal = {Physical Review. B, Condensed Matter},
title = {Singular perturbations approach to localized surface-plasmon resonance: Nearly touching metal nanospheres},
url = {http://dx.doi.org/10.1103/PhysRevB.92.235428},
volume = {92},
year = {2015}
}

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TY  - JOUR
AB  - Metallic nano-structures characterised by multiple geometric length scales support low-frequencysurface-plasmon modes, which enable strong light localisation and field enhancement. We suggestto study such configurations using singular perturbation methods, and demonstrate the efficacyof this approach by considering, in the quasi-static limit, a pair of nearly touching metallic nanospheressubjected to an incident electromagnetic wave polarised with the electric field along the lineof sphere centres. Rather than attempting an exact analytical solution, we construct the pertinent(longitudinal) eigen-modes by matching relatively simple asymptotic expansions valid in overlappingspatial domains. We thereby arrive at an effective boundary eigenvalue problem in a half-spacerepresenting the metal region in the vicinity of the gap. Coupling with the gap field gives rise to amixed-type boundary condition with varying coefficients, whereas coupling with the particle-scalefield enters through an integral eigenvalue selection rule involving the electrostatic capacitance ofthe configuration. By solving the reduced problem we obtain accurate closed-form expressions forthe resonance values of the metal dielectric function. Furthermore, together with an energy-likeintegral relation, the latter eigen-solutions yield also closed-form approximations for the induceddipolemoment and gap-field enhancement under resonance. We demonstrate agreement between theasymptotic formulae and a semi-numerical computation. The analysis, underpinned by asymptoticscaling arguments, elucidates how metal polarisation together with geometrical confinement enablesa strong plasmon-frequency redshift and amplified near-field at resonance.
AU  - Schnitzer,O
DO  - 10.1103/PhysRevB.92.235428
PY  - 2015///
SN  - 0163-1829
TI  - Singular perturbations approach to localized surface-plasmon resonance: Nearly touching metal nanospheres
T2  - Physical Review. B, Condensed Matter
UR  - http://dx.doi.org/10.1103/PhysRevB.92.235428
UR  - http://hdl.handle.net/10044/1/28113
VL  - 92
ER  -

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