Optical properties of metal nanotubes and metal nanoshells

We investigate optical properties of small composite clusters composed of a dielectric core and a metal shell (contribution of the shell dominates in the optical properties of the whole cluster). In particular, nanoshells and metal nanotubes are considered. For such shell-type particles with the shape of a sphere or a cylinder, we calculate the electron wavefunction, the electron energy and wavenumber spectrum, and the matrix elements of the corresponding optical transitions. Based on these data, we calculate the classical optical conductivity (quantum effects are ignored) and the quantum optical conductivity (relevant corrections to the classical conductivity which are caused by the quantum effects such as the electron spectrum discreteness). The oscillating nature of the dependence of these corrections on the incident light frequency is established.