Superconductivity in the PbO-type Structure alpha-FeSe

TL;DR

This paper reports the discovery of superconductivity at 8K in alpha-FeSe with a PbO-type structure, highlighting its simpler structure and potential for new superconductor research.

Contribution

It demonstrates that alpha-FeSe, a simple PbO-type structured compound, exhibits superconductivity, providing a new avenue for exploring unconventional superconductors.

Findings

Superconductivity observed at 8K in alpha-FeSe.

Superconductivity occurs only in Se-deficient samples.

Alpha-FeSe has a similar planar structure to layered oxypnictides.

Abstract

The recent discovery of superconductivity with relatively high transition temperature Tc in the layered iron-based quaternary oxypnictides La[ O1-xFx] FeAs was a real surprise. The excitement generated can be seen by the number of subsequent works published within a very short period of time. Although there exists superconductivity in alloy that contains Fe element, LaOMPn (with M= Fe, Ni; and Pn=P and As) is the first system where Fe-element plays the key role to the occurrence of superconductivity. LaOMPn has a layered crystal structure with an Fe-based plane. It is quite natural to ask whether there exists other Fe based planar compounds that exhibit superconductivity. Here we report the observation of superconductivity with zero resistance transition temperature at 8K in the PbO-type alpha-FeSe compound. Although FeSe has been studied quite extensively, a key observation is that the clean superconducting phase exists only in those samples prepared with intentional Se deficiency. What is truly striking, is that this compound has the same, perhaps simpler, planar crystal sublattice as the layered oxypnictides. Furthermore, FeSe is, compared with LaOFeAs, much easier to handle and fabricate. In view of the abundance of compounds with PbO type structure, this result opens a new route to the search for unconventional superconductors.