Effect of nematic ordering on electronic structure of FeSe.

A Fedorov,T Wolf,S V Borisenko,E Haubold,T K Kim,A Yaresko,M Hoesch,A Grüneis,B Büchner,Y Kushnirenko

doi:10.1038/srep36834

Abstract

Electronically driven nematic order is often considered as an essential ingredient of high-temperature superconductivity. Its elusive nature in iron-based superconductors resulted in a controversy not only as regards its origin but also as to the degree of its influence on the electronic structure even in the simplest representative material FeSe. Here we utilized angle-resolved photoemission spectroscopy and density functional theory calculations to study the influence of the nematic order on the electronic structure of FeSe and determine its exact energy and momentum scales. Our results strongly suggest that the nematicity in FeSe is electronically driven, we resolve the recent controversy and provide the necessary quantitative experimental basis for a successful theory of superconductivity in iron-based materials which takes into account both, spin-orbit interaction and electronic nematicity.

Highlights

Driven nematic order is often considered as an essential ingredient of high-temperature superconductivity
We further focus our attention on the electron pockets in the corners of the Brillouin Zone (BZ) and discuss the data taken along many different cuts in momentum, high-symmetry one, as in Fig. 1 panel a
Our ARPES study demonstrated that the electronic structure of FeSe is sensitive to the structural transition at 87 K, the energy scale has been overestimated earlier

Summary

Breakdown of Tetragonal Symmetry

To understand the general features of the electronic structure of FeSe in the ordered phase let us start by presenting a comparison of low temperature ARPES data and band structure calculations in Fig. 1a,b on a relatively large energy scale of hundreds of meV. Even at a first glance there is a good correspondence between the calculated in tetragonal phase (above transition) dispersions and experimental features This qualitative agreement becomes quantitative if one performs two typical for IBS transformations: orbital-dependent renormalizations and relative energy shift of the constructions in the center and the corner of the Brillouin Zone (BZ). Position of the Fermi level corresponding to the experimentally observed one is schematically indicated in Fig. 1b by the dashed green line Another effect responsible for the discrepancy between the experiment and calculations is the stronger renormalization of the dxy band. Raw data clearly indicate the presence of the features, not seen in the calculations of the tetragonal phase And this is directly seen in the energy distribution curves (EDC) shown, each of the two bottoms of the electron pockets is split, exactly as calculations predict. We found the conditions at which we resolve the components directly and they are in a remarkable agreement with the band structure calculations taking into account both, spin-orbit interaction and orthorhombic distortion

Temperature Dependence of The Electronic Structure

Conclusions

Author Contributions

Additional Information