Orbital selective insulator-metal transition in V2O3 under external pressure

TL;DR

This paper investigates the orbital-selective Mott transition in V2O3 under pressure, combining first-principles calculations with dynamical mean-field theory to explain experimental observations and quantify Coulomb interaction effects.

Contribution

It demonstrates the orbital-selective nature of the insulator-metal transition in V2O3 using LDA+DMFT and provides quantitative agreement with experimental data.

Findings

Orbital occupation switches across the transition.

Carrier effective mass increases in the paramagnetic phase.

Screened Coulomb interactions match experimental spectral functions.

Abstract

We present a detailed account of the physics of Vanadium sesquioxide (${\rm V_2O_3}$), a benchmark system for studying correlation induced metal-insulator transition(s). Based on a detailed perusal of a wide range of experimental data, we stress the importance of multi-orbital Coulomb interactions in concert with first-principles LDA bandstructure for a consistent understanding of the PI-PM MIT under pressure. Using LDA+DMFT, we show how the MIT is of the orbital selective type, driven by large changes in dynamical spectral weight in response to small changes in trigonal field splitting under pressure. Very good quantitative agreement with ($i$) the switch of orbital occupation and ($ii$) S=1 at each $V^{3+}$ site across the MIT, and ($iii$) carrier effective mass in the PM phase, is obtained. Finally, using the LDA+DMFT solution, we have estimated screening induced renormalisation of the local, multi-orbital Coulomb interactions. Computation of the one-particle spectral function using these screened values is shown to be in excellent quantitative agreement with very recent experimental (PES and XAS) results. These findings provide strong support for an orbital-selective Mott transition in paramagnetic ${\rm V_2O_3}$.