Open Access Nano Express

Terahertz plasmon and surface-plasmon modes in hollow nanospheres

Yiming Xiao1, Wen Xu12*, Yaya Zhang1 and Jiaguang Hu13

Author Affiliations

1 Department of Physics, Yunnan University, Kunming, 650091, China

2 Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, China

3 Department of Math and Physics, Wenshan University, Wenshan, 663000, China

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Nanoscale Research Letters 2012, 7:578  doi:10.1186/1556-276X-7-578

Published: 23 October 2012

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.

Keywords:
Hollow nanosphere; Electronic subband structure; Collective excitation modes; Terahertz radiation