Quantum absorption in small metal particles

TL;DR

This paper investigates how small metal particles absorb energy from electric fields, highlighting the transition from classical to quantum behavior depending on size, frequency, and energy level broadening.

Contribution

It provides a detailed analysis of electric dipole absorption considering Fermi-Thomas screening, distinguishing classical and quantum regimes based on particle size and energy parameters.

Findings

Absorption is classical when broadening or frequency exceeds mean level spacing.

Quantum absorption dominates when both broadening and frequency are below mean level spacing.

The quantum regime can be modeled as a two-level system.

Abstract

We evaluate the electric dipole absorption in small metal particles in a longitudinal electric field taking into account the Fermi-Thomas screening. When either the level broadening or the frequency of the field are larger than the mean energy-level spacing, the main contribution to absorption is classical, with quantum corrections. When both the broadening and the frequency are smaller than the mean level spacing, the absorption is manifestly quantum and can be understood in terms of the two-level system.