Electronic structure and Fermi surface of new K intercalated iron selenide superconductor KxFe2Se2

TL;DR

This study uses ab initio calculations to analyze the electronic structure and Fermi surface of KxFe2Se2, revealing the importance of potassium deficiency and structural relaxation in its superconductivity.

Contribution

It provides new insights into how potassium vacancies and structural relaxations influence the electronic properties of KxFe2Se2, a recently synthesized superconductor.

Findings

Potassium deficiency induces hole doping, crucial for superconductivity.

Structural relaxations modify the band topology.

Electronic states differ significantly from iron pnictide superconductors.

Abstract

Using the ab initio FLAPW-GGA method we examine the electronic band structure, densities of states, and the Fermi surface topology for a very recently synthesized ThCr2Si2-type potassium intercalated iron selenide superconductor KxFe2Se2. We found that the electronic state of the stoichiometric KFe2Se2 is far from that of the isostructural iron pnictide superconductors. Thus the main factor responsible for experimentally observed superconductivity for this material is the deficiency of potassium, i.e. the hole doping effect. On the other hand, based on the results obtained, we conclude that the tuning of the electronic system of the new KxFe2Se2 superconductor in the presence of K vacancies is achieved by joint effect owing to structural relaxations and hole doping, where the structural factor is responsible for the modification of the band topology, whereas the doping level determines their filling.