Linear and nonlinear optical characteristics of the Falicov-Kimball model

TL;DR

This paper investigates the optical properties of the Falicov-Kimball model, revealing conditions for second-harmonic generation and proposing an experimental test for coherence in mixed-valent systems.

Contribution

It provides a theoretical analysis of linear and nonlinear optical responses in the Falicov-Kimball model, highlighting the role of coherence in second-harmonic generation.

Findings

Second-harmonic generation requires coherence between d-electrons and f-holes.

No second-harmonic generation occurs when f-site occupation is a good quantum number.

Proposes measuring dynamic second-order susceptibility as an experimental test.

Abstract

We calculate the linear and nonlinear optical properties of the Falicov-Kimball model for a mixed-valent system within the self-consistent mean-field approximation. Second-harmonic generation can only occur if the mixed-valent state has a built-in coherence between the itinerant d-electrons and the localized f-holes. By contrast, second-harmonic generation cannot occur for solutions of the model with f-site occupation as a good quantum number. As an experimental test of coherence in mixed-valent compounds we propose a measurement of the dynamic second-order susceptibility.