Pygmy resonances in artificial nuclei far-infrared absorption by electron-hole droplets

Abstract

The structure of E1 resonances has been examined in a microscopic random phase approximation calculation for neutral, symmetric, closed shell and electron-hole systems in a quantum dot. The number of electron-hole pairs, N, is varied from 6 to 42. The occurrence of small, but distinct, E1 peaks in the far-infrared spectra located in the low energy tail of the giant dipole resonance consisting of highly coherent electron-hole excitations is predicted. These pygmy resonances account for about 2% of the dipole energy-weighted photoabsorption sum rule. A very weak dependence of the average pygmy resonance energy on the number of electron-hole pairs is found.