Transfer of Spectral Weight in Spectroscopies of Correlated Electron Systems

TL;DR

This paper investigates how spectral weight shifts in the spectra of strongly correlated electron systems, comparing models and experimental data to understand phenomena in metals, insulators, and Kondo insulators.

Contribution

It provides a comparative analysis of spectral weight transfer in Hubbard and periodic Anderson models, linking theoretical predictions with experimental observations in correlated materials.

Findings

Anomalous optical spectral weight enhancement in correlated metals like V2O3.

Excellent agreement between model predictions and experimental data for insulating phases.

The periodic Anderson model explains energy scales in Kondo insulators but cannot account for large scattering rates.

Abstract

We study the transfer of spectral weight in the photoemission and optical spectra of strongly correlated electron systems. Within the LISA, that becomes exact in the limit of large lattice coordination, we consider and compare two models of correlated electrons, the Hubbard model and the periodic Anderson model. The results are discussed in regard of recent experiments. In the Hubbard model, we predict an anomalous enhancement optical spectral weight as a function of temperature in the correlated metallic state which is in qualitative agreement with optical measurements in $V_2O_3$. We argue that anomalies observed in the spectroscopy of the metal are connected to the proximity to a crossover region in the phase diagram of the model. In the insulating phase, we obtain an excellent agreement with the experimental data and present a detailed discussion on the role of magnetic frustration by studying the $k-$resolved single particle spectra. The results for the periodic Anderson model are discussed in connection to recent experimental data of the Kondo insulators $Ce_3Bi_4Pt_3$ and $FeSi$. The model can successfully explain the different energy scales that are associated to the thermal filling of the optical gap, which we also relate to corresponding changes in the density of states. The temperature dependence of the optical sum rule is obtained and its relevance for the interpretation of the experimental data discussed. Finally, we argue that the large scattering rate measured in Kondo insulators cannot be described by the periodic Anderson model.