Low-dimensional plasmons in atom-scale metallic objects

Abstract

Examples of plasmonic excitations in atomically thin metal films and wires are presented. The low-energy electron energy loss spectroscopy with high momentum and energy resolutions allows us to determine the strongly dispersing low-energy collective excitation from mid-to near-infrared frequency range with momentum range up to ∼0.1 Å -1 . The dispersion relation is far apart from the light line and strongly reflects the shape and size effects in nanometer to Ångstrom scale. The two-dimensional type plasmon is observed in metallic atom sheets and the one-dimensional type plasmons are also measured from some metallic atom chains. From the direct measurement of their plasmonic band dispersion, we are able to detect the carrier doping effect, electronic correlation effect, and Rashba-spin-orbit splitting effect in these ultimately tiny systems.