Temperature-dependent full spectrum dielectric function of semiconductors from first principles
Zherui Han, Changkyun Lee, Jiawei Song, Haiyan Wang, Peter Bermel, Xiulin Ruan
Abstract
From the ultraviolet to the mid-infrared region, light-matter interaction mechanisms in semiconductors progressively shift from electronic transitions to phononic resonances and are affected by temperature. Here, we present a unified temperature-dependent treatment of both electrons and phonons entirely from first principles, enabling the prediction of a full-spectrum dielectric function with ${\mathrm{CeO}}_{2}$ as the prototype material. At elevated temperatures, ab initio molecular dynamics is employed to find thermal perturbations to electronic structures and construct effective force constants describing potential energy surface. Four-phonon scattering and phonon renormalization are included in an integrated manner in this approach. Our first-principles-calculated refractive index of ${\mathrm{CeO}}_{2}$ agrees well with measured data from literature and our own temperature-dependent ellipsometer experiment.