Polaron transport and Verwey transition in magnetite

TL;DR

This paper models polaron transport in magnetite to explain the Verwey transition, showing no band structure change but observing trimeron hopping, and matches experimental conductivity data.

Contribution

It introduces an ab initio-based model combining kinetic Monte Carlo and molecular dynamics to describe polaron-lattice interactions in magnetite.

Findings

No significant band structure change across the transition.

Observation of trimeron hopping.

Model reproduces experimental dc-conductivity.

Abstract

The enigmatic puzzle of the Verwey transition in magnetite Fe$_3$O$_4$ has been unresolved for almost a century. We present an ab initio-based model of the polaron transport combining kinetic Monte Carlo and molecular dynamics calculations to directly describe the coupling of polarons with lattice vibrations. Contrary to the Ihle-Lorentz small-polaron model, we find no significant change in the band structure across the Verwey transition, however, trimeron hopping is observed. The proposed model provides dc-conductivity in agreement with experimental data across the Verwey transition.