Optical probes of electron correlations in solids

TL;DR

This paper reviews optical spectroscopy techniques and their application in probing electron correlations in solids, emphasizing the quantum mechanical framework and the interpretation of experimental data through sum rules and interaction effects.

Contribution

It provides a comprehensive overview of optical probes for electron correlations, integrating classical and quantum descriptions and discussing the impact of interactions on optical spectra.

Findings

Optical techniques can reveal strong electron correlation effects.

Sum rules are essential for interpreting optical spectra.

Interactions between electrons and collective modes significantly influence optical responses.

Abstract

Classically the interaction between light and matter is given by the Maxwell relations. These are briefly reviewed and will be used as a basis to discuss several techniques that are used in optical spectroscopy. We then discuss the quantum mechanical description of the optical conductivity based on the Kubo formalism. This is used as a basis to understand how strong correlation effects can be observed using optical techniques. We will discuss the use of sum rules in the interpretation of optical experiments. Finally, we describe the effect of including interactions between electronic and collective degrees of freedom on optical spectra.