Synthesis and crystal growth of Cs0.8(FeSe0.98)2: a new iron-based superconductor with Tc=27K

TL;DR

This paper reports the synthesis and structural analysis of a new iron-based superconductor Cs0.8(FeSe0.98)2 with a Tc of 27K, comparing its properties to related compounds and exploring the relationship between structure and superconductivity.

Contribution

The study introduces a new Cs-intercalated FeSe superconductor and provides detailed structural and magnetic characterization, expanding understanding of alkali metal intercalated iron selenides.

Findings

Cs0.8(FeSe0.98)2 has Tc=27.4K, slightly lower than KxFe2Se2.

The unit cell volume increases when replacing K with Cs.

Tc correlates with anion height similarly to other Fe-superconductors.

Abstract

We report on the synthesis of large single crystals of a new FeSe-layer superconductor Cs0.8(FeSe0.98)2. X-ray powder diffraction, neutron powder-diffraction and magnetization measurements have been used to compare the crystal structure and the magnetic properties of Cs0.8(FeSe0.98)2 with those of the recently discovered potassium intercalated system KxFe2Se2. The new compound Cs0.8(FeSe0.98)2 shows a slightly lower superconducting transition temperature (Tc=27.4 K) in comparison to 29.5 in K0.8(FeSe0.98)2). The volume of the crystal unit cell increases by replacing K by Cs - the c-parameter grows from 14.1353(13) {\AA} to 15.2846(11) {\AA}. For the so far known alkali metal intercalated layered compounds (K0.8Fe2Se2 and Cs0.8(FeSe0.98)2) the Tc dependence on the anion height (distance between Fe-layers and Se-layers) was found to be analogous to those reported for As-containing Fe-superconductors and Fe(Se1-xChx), where Ch=Te, S.