Electrodynamics of the vanadium oxides VO2 and V2O3

TL;DR

This study investigates the optical properties of VO2 and V2O3 across their metal-insulator transitions, highlighting the role of electronic correlations and observing sharp optical features linked to their electronic structures.

Contribution

It provides detailed optical measurements of VO2 and V2O3, demonstrating the significance of electronic correlations in their phase transitions and identifying specific optical features related to their electronic states.

Findings

Significant changes in optical conductivity across phase transitions.

Evidence of electronic correlations affecting charge carrier kinetic energy.

Observation of a sharp optical transition in insulating VO2.

Abstract

The optical/infrared properties of films of vanadium dioxide (VO2) and vanadium sesquioxide (V2O3) have been investigated via ellipsometry and near-normal incidence reflectance measurements from far infrared to ultraviolet frequencies. Significant changes occur in the optical conductivity of both VO2 and V2O3 across the metal-insulator transitions at least up to (and possibly beyond) 6 eV. We argue that such changes in optical conductivity and electronic spectral weight over a broad frequency range is evidence of the important role of electronic correlations to the metal-insulator transitions in both of these vanadium oxides. We observe a sharp optical transition with possible final state (exciton) effects in the insulating phase of VO2. This sharp optical transition occurs between narrow a1g bands that arise from the quasi-one-dimensional chains of vanadium dimers. Electronic correlations in the metallic phases of both VO2 and V2O3 lead to reduction of the kinetic energy of the charge carriers compared to band theory values, with paramagnetic metallic V2O3 showing evidence of stronger correlations compared to rutile metallic VO2.