Superconductivity in LiOHFeS single crystals with a shrunk c-axis lattice constant

TL;DR

This study reports the synthesis of LiOHFeS single crystals with superconductivity at 2.8 K, highlighting a shrunk c-axis lattice and near charge neutrality, providing insights into its structural and magnetic properties.

Contribution

First successful growth of superconducting LiOHFeS crystals with a shrunk c-axis, revealing structural differences and low upper critical field compared to similar compounds.

Findings

Superconductivity at 2.8 K in LiOHFeS crystals.

Shrunk c-axis lattice in superconducting phase.

Low upper critical magnetic field.

Abstract

By using a hydrothermal ion-exchange method, we have successfully grown superconducting crystals of LiOHFeS with ${T_c}$ of about 2.8 K. Being different from the sister sample (Li${_{1-x}}$Fe${_x}$)OHFeSe, the energy dispersion spectrum analysis on LiOHFeS shows that the Fe/S ratio is very close to 1:1, suggesting an almost charge neutrality and less electron doping in the FeS planes of the system. Comparing with the non superconducting LiOHFeS crystal, each peak of the X-ray diffraction pattern of the superconducting crystal splits into two, and the diffraction peaks locating at lower reflection angles are consistent with that of non-superconducting ones. The rest set of diffraction peaks with higher reflection angles is corresponding to the superconducting phase, suggesting that the superconducting phase may has a shrunk c-axis lattice constant. Magnetization measurements indicate that the magnetic shielding due to superconductivity can be quite high under a weak magnetic field. The resistivity measurements under various magnetic fields show that the upper critical field is quite low, which is similar to the tetragonal FeS superconductor.