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Thursday, March 19, 2015

Optical Forces on Silver Homogeneous Nanotubes: Study of Shell Plasmonic Interaction

R. M. Abraham Ekeroth, M. F. Lester

In previous works (Abraham et al., Plasmonics 6(3):435–444 (2011); Abraham Ekeroth and Lester, Plasmonics 7(4):579–587, (2012); Abraham Ekeroth and Lester, Plasmonics 8:1417–1428 (2013)), we performed an exhaustive study about optical properties of metallic realistic nanotubes, hollow or with dielectric cores. Based on rigorous calculations, involving experimental-interpolated dielectric functions, we pointed out the importance of using an adequate size-corrected dielectric function in homogeneous bidimensional metallic shells when their thicknesses are about several nanometers. In this paper, we compute optical forces induced by electromagnetic plane waves on these kind of nanostructures. We focus the study under p polarisation, in order to observe plasmonic-related behaviour. The optical forces are calculated by the Maxwell’s stress tensor without any kind of approximation. We show three examples of mechanical effects on silver thin shells. The characteristics of the electromagnetic interaction in these structures, from the point of view of forces, allow us to comprehend the problem of the plasmonic interaction in the shell in a new way. We show numerically, for the first time, the nature of bonding/antibonding of surface plasmons in nanotubes made of realistic materials, in a way independent of approximations related to scale. The behaviour of the realistic silver shells is compared with the features deduced from the plasmon hybridization model, which are predicted from a quasi-static approximation of electromagnetic response. Our results conceive a full retarded problem and can only contain numerical errors. In addition, we compare rigorous calculations for the optical forces with those ones obtained from the far field approach, when specified for shell geometry.

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