Terahertz conductivity and coupling between geometrical and plasmonic resonances in nanostructures

Abstract

Terahertz conductivity spectra of charges moving ballistically in one-, two-, and three-dimensional infinitely deep rectangular potential wells were investigated theoretically using semiclassical and quantum Kubo formulas. The conductivity spectrum of a degenerate electron gas in these nanostructures exhibits a series of geometrical resonances. These further couple with plasmon resonances occurring in isolated structures: qualitatively different interaction regimes are found in one-, two-, and three-dimensional nanostructures. In contrast, the response of a nondegenerate electron gas smears into a single broad band due to the excessive spectral broadening caused by the wide distribution of charge velocities.