Optical response of metallic and insulating VO2 calculated with the LDA approach

TL;DR

This study uses the LDA approach to calculate and analyze the optical response of metallic and insulating VO2, explaining spectral features and the metal-insulator transition with good agreement to experimental data.

Contribution

It provides a detailed LDA-based calculation of VO2's optical properties, including spectral features and transition mechanisms, highlighting the effects of the metal-insulator transition.

Findings

Reproduces energy positions and intensities of spectral features

Explains the spectral differences across the metal-insulator transition

Identifies a 0.6 eV shift due to LDA underestimation of the band gap

Abstract

We calculated the optical response of metallic and insulating VO2 using the LDA approach. The band structure calculation was based in the full-potential linear-muffin-tin method. The imaginary part of the dielectric function e2(w) is related to the different optical transitions. The Drude tail in the calculation of the metallic phase corresponds to intra-band d-d transitions. The calculation in the insulating phase is characterized by the transitions to the d||* band. The low frequency features, 0.0-5.0 eV, correspond to V 3d-V 3d transitions, whereas the high frequency structures, 5.0-12 eV, are related to O 2p-V 3d transitions. The calculation helps to explain the imaginary part of the dielectric function e2(w), as well as the electron-energy-loss and reflectance spectra. The results reproduce not only the energy position and relative intensity of the features in the spectra, but also the main changes across the metal-insulator transition and the polarization dependence. The main difference is a shift of about 0.6 eV in the calculation of the insulating phase. This discrepancy arises because the LDA calculation underestimates the value of the band gap.