High-energy photoemission on Fe3O4: Small polaron physics and the Verwey transition

TL;DR

This study investigates the electronic structure and charge ordering in Fe3O4 using soft x-ray photoemission, revealing small polaron behavior and insights into the Verwey transition involving Jahn-Teller effects and Coulomb interactions.

Contribution

It provides new experimental evidence distinguishing surface and bulk effects and links small polaron physics to the Verwey transition in magnetite.

Findings

Evidence for strongly bound small polarons from spectral and conductivity data.

Temperature-dependent pseudogap behavior supports polaronic charge dynamics.

Findings suggest the Verwey transition involves cooperative Jahn-Teller effects stabilized by Coulomb interactions.

Abstract

We have studied the electronic structure and charge ordering (Verwey) transition of magnetite (Fe3O4) by soft x-ray photoemission. Due to the enhanced probing depth and the use of different surface preparations we are able to distinguish surface and volume effects in the spectra. The pseudogap behavior of the intrinsic spectra and its temperature dependence give evidence for the existence of strongly bound small polarons consistent with both dc and optical conductivity. Together with other recent structural and theoretical results our findings support a picture in which the Verwey transition contains elements of a cooperative Jahn-Teller effect, stabilized by local Coulomb interaction.