Orbital Switching and the First-Order Insulator-Metal Transition in Paramagnetic V_2O_3

TL;DR

This paper uses ab-initio LDA+DMFT calculations to explain the pressure-driven first-order metal-insulator transition in paramagnetic V₂O₃, highlighting orbital switching and structural changes.

Contribution

It introduces a new picture where pressure-induced decrease of trigonal distortion explains the MIT, aligning well with experimental observations.

Findings

Orbital occupation switches across the MIT.

Good agreement with resistivity and spectral data.

Pressure reduces trigonal distortion in the strong correlation regime.

Abstract

The first-order metal-insulator transition (MIT) in paramagnetic $V_{2}O_{3}$ is studied within the ab-initio scheme LDA+DMFT, which merges the local density approximation (LDA) with dynamical mean field theory (DMFT). With a fixed value of the Coulomb $U=6.0 eV$, we show how the abrupt pressure driven MIT is understood in a new picture: pressure-induced decrease of the trigonal distortion within the strong correlation scenario (which is not obtained within LDA). We find good quantitative agreement with $(i)$ switch of the orbital occupation of $(a_{1g},e_{g1}^{\pi}, e_{g2}^{\pi})$ and the spin state S=1 across the MIT, $(ii)$ thermodynamics and $dc$ resistivity, and $(iii)$ the one-electron spectral function, within this new scenario.