Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2

TL;DR

This paper reports the discovery of bulk superconductivity at 38 K in hole-doped BaFe2As2 by potassium substitution, expanding the class of iron arsenide superconductors with a ThCr2Si2-type structure.

Contribution

It demonstrates that hole doping in BaFe2As2 induces high-temperature superconductivity, establishing a new oxygen-free iron arsenide superconductor with the highest Tc among similar compounds.

Findings

Superconductivity at 38 K achieved in (Ba1-xKx)Fe2As2

Hole doping suppresses SDW anomaly and induces superconductivity

Expands iron arsenide superconductor family with ThCr2Si2 structure

Abstract

The ternary iron arsenide BaFe2As2 becomes superconducting by hole doping, which was achieved by partial substitution of the barium site with potassium. We have discovered bulk superconductivity up to Tc = 38 K in (Ba1-xKx)Fe2As2 with x = 0.4. The parent compound BaFe2As2 as well as KFe2As2 both crystallize in the tetragonal ThCr2Si2-type structure, which consists of (FeAs)- iron arsenide layers separated by barium or potassium ions. BaFe2As2 is a poor metal and exhibits a SDW anomaly at 140 K. By substituting Ba2+ for K+ ions we have introduced holes in the (FeAs)- layers, which suppress the SDW anomaly and induce superconductivity. This scenario is very similar to the recently discovered arsenide-oxide superconductors. The Tc of 38 K in (Ba1-xKx)Fe2As2 is the highest observed critical temperature in hole doped iron arsenide superconductors so far. Therefore, we were able to expand this class of superconductors by oxygen-free compounds with the ThCr2Si2-type structure. Our results suggest, that superconductivity in these systems essentially evolves from the (FeAs)- layers and may occur in other related compounds.