Surface plasmon lifetime in metal nanoshells

The lifetime of localized surface plasmon plays an important role in many aspects of plasmonics and its applications. In small metal nanostructures, the dominant mechanism of plasmon decay is size-dependent Landau damping. We performed quantum-mechanical calculations of Landau damping for the bright surface plasmon mode in a metal nanoshell with dielectric core. In contrast to the conventional model based on the electron surface scattering, we found that the damping rate decreases as the nanoshell thickness is reduced. The origin of this behavior is traced to the spatial distribution of plasmon local field in the metal shell. We also found that, due to the interference of electron scattering amplitudes from the two nanoshell metal surfaces, the damping rate exhibits pronounced quantum beats with changing shell thickness.