Model of Electronic Structure and Superconductivity in Orbitally Ordered FeSe

TL;DR

This paper models the electronic structure and superconductivity in FeSe, showing how orbital order explains various experimental observations, including band structure, spin properties, and superconducting gap features.

Contribution

It introduces a band structure model with orbital order that aligns with recent experimental data and explains superconducting and electronic properties of FeSe.

Findings

Consistent band structure with photoemission and quantum oscillations

Superconducting gap with nodes on electron pockets

Temperature dependence of Knight shift and spin relaxation

Abstract

We provide a band structure with low-energy properties consistent with recent photoemission and quantum oscillations measurements on FeSe, assuming mean-field like s and/or d-wave orbital ordering at the structural transition. We show how the resulting model provides a consistent explanation of the temperature dependence of the measured Knight shift and the spin-relaxation rate. Furthermore, the superconducting gap structure obtained from spin fluctuation theory exhibits nodes on the electron pockets, consistent with the 'V'-shaped density of states obtained by tunneling spectroscopy on this material, and the temperature dependence of the London penetration depth. Our studies prove that the recent experimental observations of the electronic properties of FeSe are consistent with orbital order, but leave open the microscopic origin of the unusual band structure of this material.