title: Terahertz plasmon and surface-plasmon modes in hollow nanospheres.
abstract: : We present a theoretical study of the electronic subband structure and collective electronic excitation associated with plasmon and surface plasmon modes in metal-based hollow nanosphere. The dependence of the electronic subband energy on the sample parameters of the hollow nanosphere is examined. We find that the subband states with different quantum numbers l degenerate roughly when the outer radius of the sphere is r2 ≥ 100 nm. In this case, the energy spectrum of a sphere is mainly determined by quantum number n. Moreover, the plasmon and surface plasmon excitations can be achieved mainly via inter-subband transitions from occupied subbands to unoccupied subbands. We examine the dependence of the plasmon and surface-plasmon frequencies on the shell thickness d and the outer radius r2 of the sphere using the standard random-phase approximation. We find that when a four-state model is employed for calculations, four branches of the plasmon and surface plasmon oscillations with terahertz frequencies can be observed, respectively.
authors.affiliation: Department of Physics, Yunnan University, Kunming, 650091, China. wenxu_issp@yahoo.cn.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Xiao
authors.forename: Wen
authors.initials: W
authors.lastname: Xu
authors.forename: Yaya
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jiaguang
authors.initials: J
authors.lastname: Hu