Dipole matrix element approach vs. Peierls approximation for optical conductivity

TL;DR

This paper compares the full dipole matrix element calculation with the Peierls approximation for optical conductivity in transition metal oxides, showing the approximation's limitations at higher energies.

Contribution

The authors develop a computational method within Wien2K to evaluate optical conductivity and systematically compare the dipole matrix element approach with the Peierls approximation.

Findings

Peierls approximation works well for d-d transitions at low frequencies

Peierls approximation fails for p-d transitions at higher energies

Full dipole matrix calculations are necessary for accurate optical spectra at higher frequencies

Abstract

We develop a computational approach for calculating the optical conductivity in the augmented plane wave basis set of Wien2K and apply it for thoroughly comparing the full dipole matrix element calculation and the Peierls approximation. The results for SrVO3 and V2O3 show that the Peierls approximation, which is commonly used in model calculations, works well for optical transitions between the d orbitals. In a typical transition metal oxide, these transitions are solely responsible for the optical conductivity at low frequencies. The Peierls approximation does not work, on the other hand, for optical transitions between p- and d-orbitals which usually became important at frequencies of a few eVs