Enhanced quality factor in silver nanotubes

We have numerically evaluated the complex valued eigenfrequencies of infinite silver nanotubes as a function of the ratio of internal and external radius, by solving the surface plasmon dispersion relations for the TE polarization. The results are shown for tubes of external radius of 20 nm, 50 nm, 100 nm, 150 nm, 200 nm and 300 nm with the internal radius varying from 0.1 to 0.9 fractions of the external radius. We have observed that their quality factor Q is substantially enhanced as compared to solid cylinders or wires.