Hubbard energy dependence of electronic structures in rare-earth monoxides

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 (~ 1 × 10⁻⁴), even a few meV modulations in U are sufficient for a detectable spectral response.