Theoretical Models for the Optical Properties of Clusters and Nanostructures

Abstract

Applications of the Time Dependent Density Functional Formalism to calculate the response of metallic and semiconducting nanostructures to static and time-dependent electric fields in the linear regime are reviewed. The paper focuses on the presentation of models of increasing sophistication for the cluster structure, ranging from the simple spherical jellium model to a fully ab initio description of the ionic structure. Simple models explain the main features of the spectrum. For instance the existence of a pronounced surface plasmon resonance in the absorption spectrum of alkali metal clusters, and its redshift with respect to the classical Mie resonance are well explained within the framework of the simple jellium model. However, the detailed understanding of the experimental optical spectra can only be achieved by complementary ab initio calculations. In fact, the optical spectrum appears to carry detailed information on the cluster structure. Details of the new theories and computational schemes to deal with the optical properties of complex systems are also presented: linear and nonlinear susceptibilities, quasiparticle excitations, core-polarization. These methods are of relevance in the physics of nanostructures and nanoscale technology.