Uncovering the mechanism of the impurity-selective Mott transition in paramagnetic V$_{2}$O$_{3}$

TL;DR

This paper reveals that impurity-induced local symmetry breaking, rather than chemical pressure, drives the Mott transition in V$_{2}$O$_{3}$, highlighting the importance of local environment effects in correlated materials.

Contribution

It demonstrates through combined DFT and DMFT calculations that defect-induced local symmetry breaking explains the impurity-selective Mott transition in V$_{2}$O$_{3}$, challenging previous pressure-based explanations.

Findings

Cr and Ti dopants differently affect local symmetry and correlations.

The phase diagram changes are driven by defect-induced local symmetry breaking.

Accurate modeling of the one-electron Hamiltonian is crucial for understanding correlations.

Abstract

While the phase diagrams of the one- and multi-orbital Hubbard model have been well studied, the physics of real Mott insulators is often much richer, material dependent, and poorly understood. In the prototype Mott insulator V$_{2}$O$_{3}$, chemical pressure was initially believed to explain why the paramagnetic-metal to antiferromagnetic-insulator transition temperature is lowered by Ti doping while Cr doping strengthens correlations, eventually rendering the high-temperature phase paramagnetic insulating. However, this scenario has been recently shown both experimentally and theoretically to be untenable. Based on full structural optimization, we demonstrate via the charge self-consistent combination of density functional theory and dynamical mean-field theory that changes in the V$_{2}$O$_{3}$ phase diagram are driven by defect-induced local symmetry breakings resulting from dramatically different couplings of Cr and Ti dopants to the host system. This finding emphasizes the high sensitivity of the Mott metal-insulator transition to the local environment and the importance of accurately accounting for the one-electron Hamiltonian, since correlations crucially respond to it.