The electronic structure and magnetic phase transition of hexagonal FeSe thin films studied by photoemission spectroscopy

TL;DR

This study investigates the electronic structure and magnetic phase transition of hexagonal FeSe thin films grown on SrTiO3, revealing a temperature-driven magnetic transition around 300 K linked to electronic structure changes.

Contribution

First detailed analysis of the electronic structure of hexagonal FeSe, demonstrating a magnetic phase transition driven by electronic structure reconstruction.

Findings

Hexagonal FeSe is metallic and electron doped with six elliptical electron pockets.

Band shifts indicate a magnetic transition around 300 K.

Fermi surface topology remains largely unchanged with film thickness.

Abstract

Hexagonal FeSe thin films were grown on SrTiO3 substrates and the temperature and thickness dependence of their electronic structures were studied. The hexagonal FeSe is found to be metallic and electron doped, whose Fermi surface consists of six elliptical electron pockets. With decreased temperature, parts of the bands shift downward to high binding energy while some bands shift upwards to EF. The shifts of these bands begin around 300 K and saturate at low temperature, indicating a magnetic phase transition temperature of about 300 K. With increased film thickness, the Fermi surface topology and band structure show no obvious change except some minor quantum size effect. Our paper reports the first electronic structure of hexagonal FeSe, and shows that the possible magnetic transition is driven by large scale electronic structure reconstruction.