Infrared properties of heavy-fermions: evolution from weak to strong hybridizations

TL;DR

This paper reviews how charge excitations in heavy fermion compounds evolve with hybridization strength, highlighting the applicability of the periodic Anderson model across different materials.

Contribution

It provides a detailed analysis of infrared properties in heavy fermions, emphasizing the relationship between hybridization strength and charge excitations, supported by experimental data.

Findings

Scaling between hybridization energy gap and hybridization strength confirmed

Periodic Anderson model effectively describes low-energy charge excitations

Charge excitation behavior varies with hybridization in different compounds

Abstract

In this article, we review the charge excitations of heavy fermion compounds probed by infrared spectroscopy. The article is not meant to be a comprehensive survey of experimental investigations. Rather it focuses on the dependence of charge excitations on the hybridization strength. In this context, the infrared properties of the Ce$_m$M$_n$In$_{3m+2n}$ family are discussed in detail since the hybridization strengths differ dramatically in different members despite their similar lattice structures. Investigations on some mixed valent compounds are also presented aiming to elucidate the generic trend on the evolution. In particular, we address the scaling between hybridization energy gap $\Delta_{dir}$ and the hybridization strength $\tilde{V}$($\propto\sqrt{WT_K}$) in a wide range of heavy fermions compounds which demonstrates that the periodic Anderson model can generally and quantitatively describe the low-energy charge excitations.