Magnetic Moment Collapse-Driven Mott Transition in MnO

TL;DR

This paper investigates the Mott transition in MnO, revealing that a collapse of magnetic moment driven by crystal field effects, rather than bandwidth changes, causes the insulator-to-metal transition under pressure.

Contribution

It demonstrates that magnetic moment collapse, driven by crystal field splitting, is the key mechanism for the Mott transition in MnO, challenging previous bandwidth-centric views.

Findings

Reproduces the simultaneous moment, volume, and metallization transition in MnO.

Identifies magnetic moment collapse due to crystal field splitting as the transition mechanism.

Shows the transition is not primarily driven by bandwidth variation.

Abstract

The metal-insulator transition in correlated electron systems, where electron states transform from itinerant to localized, has been one of the central themes of condensed matter physics for more than half a century. The persistence of this question has been a consequence both of the intricacy of the fundamental issues and the growing recognition of the complexities that arise in real materials, even when strong repulsive interactions play the primary role. The initial concept of Mott was based on the relative importance of kinetic hopping (measured by the bandwidth) and on-site repulsion of electrons. Real materials, however, have many additional degrees of freedom that, as is recently attracting note, give rise to a rich variety of scenarios for a ``Mott transition.'' Here we report results for the classic correlated insulator MnO which reproduce a simultaneous moment collapse, volume collapse, and metallization transition near the observed pressure, and identify the mechanism as collapse of the magnetic moment due to increase of crystal field splitting, rather than to variation in the bandwidth.