Characteristics of low-dimensional plasmons in a metallic strip monolayer on a semiconductor surface

Abstract

By means of the time-dependent local-density approximation, we investigate low-dimensional plasmons (LDPL's) in a metallic strip monolayer on a semiconductor surface, namely, LDPL's in a two-dimensional conduction-electron system confined in a strip region. We analyze the energy-loss intensity, the energy dispersion, and the induced-charge distribution of the two plasmon modes at each wave number q along the strip. When the wavelength \ensuremath{\lambda} $(=2\ensuremath{\pi}/q)$ of the mode is considerably smaller than the strip width D, the higher-energy mode (HEM) has a definite character of the area plasmon (APL), and its energy is close to that of the two-dimensional plasmon in an infinite area (pure 2DPL). However, as the mode energy deviates upward from that of the pure 2DPL with an increase in \ensuremath{\lambda}, the induced-charge distribution of the APL evolves into a standing-wave pattern with its free end at the edge. In contrast, the lower-energy mode (LEM) has a definite character of the edge plasmon. When \ensuremath{\lambda} is small compared with D, the induced charge density of the LEM decays slowly on the inside of the strip owing to the influence of the HEM (APL) close to the LEM in energy.