Observation of Dirac Cone Band Dispersion in FeSe Thin Films by Photoemission Spectroscopy

TL;DR

This study uses ARPES to observe Dirac cone band dispersions in FeSe thin films, revealing their coexistence with nematicity and potential link to spin degrees of freedom.

Contribution

First observation of Dirac cone dispersions in FeSe thin films and analysis of their evolution with temperature, thickness, and doping.

Findings

Dirac cones exist below nematic transition temperature

Dirac cones disappear when nematicity is suppressed

Spin degrees of freedom may influence nematicity in FeSe

Abstract

The electronic structure of FeSe thin films grown on SrTiO3 substrate is studied by angle-resolved photoemission spectroscopy (ARPES). We reveal the existence of Dirac cone band dispersions in FeSe thin films thicker than 1 Unit Cell below the nematic transition temperature, whose apex are located -10 meV below Fermi energy. The evolution of Dirac cone electronic structure for FeSe thin films as function of temperature, thickness and cobalt doping is systematically studied. The Dirac cones are found to be coexisted with the nematicity in FeSe, disappear when nematicity is suppressed. Our results provide some indication that the spin degrees of freedom may play some kind of role in the nematicity of FeSe.