Conductivity of a small metallic particle

The size‐dependent ac‐conductivity of a small metallic particle is studied for electrons enclosed in a box with random impurities. The exact wave functions and energies are calculated numerically up to 500 electrons, then the Kubo‐formula is evaluated, and an ensemble average is performed. A strong size‐ and frequency dependence of the conductivity is found which is in good agreement with random matrix results. The size dependence of the dc‐conductivity agrees qualitatively with microwave absorption measurements on submicron particles.