Hubbard energy dependence of electronic structures in rare-earth monoxides

TL;DR

This study investigates how subtle structural changes can alter the Hubbard energy ($U$) in rare-earth monoxides and affect their optical properties, revealing that small $U$ modulations are detectable via differential spectroscopy.

Contribution

It provides a theoretical analysis of the $U$ energy dependence on optical spectra in LuO, highlighting the impact of $U$ variations on optical responses and the detectability of these changes.

Findings

$U$ energy influences differential transmission and reflectivity spectra.

Small modulations in $U$ (~few meV) are detectable with current spectroscopy.

$U$-induced plasma energy changes affect optical properties.

Abstract

To realize the significant potential of optical materials such as strongly electron-correlated open-shell rare-earth monoxides, understanding the electron-localization Hubbard parameters ($U$) is of central importance. The Hubbard energy is believed to be material specific and constant. However, it has recently been pointed out that even subtle structural changes can induce changes in $U$ parameters. For LuO, we theoretically evaluated $U$ energy dependence of the differential transmission and reflectivity spectra to assess the impact of $U$ energy on the optical properties. In addition to the conventional derivative-like contribution, we observed the influence of the Drude tail owing to $U$-induced plasma energy modulation. Given the typical detection sensitivity of differential spectroscopy ($\sim 1 \times 10^{-4}$), even a few meV modulations in $U$ are sufficient for a detectable spectral response.