Plasmon Resonance Wavelengths of Circular Metal Nanowires with Account of Losses

We investigate the resonances in the scattering and absorption of the TE-polarized light by the solid silver, gold and copper wires of nanoscale diameter and circular cross-section. Here we use the analytical solution and experimental data for the metal complex permittivity function in the visible range. We find that the well-known textbook equation for the wavelength of the localized surface plasmon (LSP) resonances is valid for a silver cylinder but not for gold and copper ones. The reason is different values of losses in these metals: gold and copper have much larger values of imaginary part of the relative permittivity in the visible range than silver. This shifts the LSP resonances to considerably longer wavelengths. We present a simple modified equation for finding these wavelengths.