Structural transition and superconductivity in hydrothermally synthesized FeX (X = S, Se)

TL;DR

This study compares the structural and superconducting properties of hydrothermally synthesized FeX compounds, revealing that structural transitions influence superconductivity in FeSe but not in FeS.

Contribution

It provides new insights into how hydrothermal synthesis affects the crystal structure and superconductivity of FeSe and FeS, highlighting the role of low-temperature structural phases.

Findings

Hydrothermal FeSe is non-superconducting and transforms to a triclinic structure at 60 K.

Hydrothermal FeS is superconducting at 4.8 K with no structural transition.

Structural differences are linked to the presence or absence of superconductivity.

Abstract

Tetragonal beta-FeSe obtained by hydrothermal reaction is not superconducting and transforms to a triclinic structure at 60 K unlike superconducting FeSe from solid state synthesis, which becomes orthorhombic at 90 K. In contrast, tetragonal iron sulphide FeS from hydrothermal synthesis is superconducting at 4.8 K but undergoes no structural transition. Our results suggest that the absence of superconductivity in hydrothermally synthesized FeSe may be associated to the low-temperature structure with zigzag chains of iron atoms, which is different from the known orthorhombic Cmme structure of superconducting FeSe.