Pressure effect on superconductivity in FeSe0.5Te0.5

TL;DR

This study investigates how applying pressure affects the superconducting transition temperature and structural phases of FeSe0.5Te0.5, revealing a pressure-induced Tc increase, a plateau, and eventual suppression linked to a structural phase transition.

Contribution

It provides new insights into the pressure dependence of Tc and structural changes in FeSe0.5Te0.5, highlighting similarities with FeSe and elucidating the role of structural transitions in superconductivity.

Findings

Tc increases from 13.5 K to 19.5 K under pressure

Superconductivity disappears around 7.0 GPa due to structural transition

Structural phase change from tetragonal to hexagonal occurs under high pressure

Abstract

Due to the simple layered structure, isostructural FeSe and FeSe0.5Te0.5 are clue compounds for understanding the principal mechanisms of superconductivity in the family of Fe-based superconductors. High-pressure magnetic, structural and M\"ossbauer studies have been performed on single-crystalline samples of superconducting FeSe0.5Te0.5 with Tc = 13.5 K. Susceptibility data have revealed a strong increase of Tc up to 19.5 K for pressures up to 1.3 GPa, followed by a plateau in the Tc(p) dependence up to 5.0 GPa. Further pressure increase leads to a disappearance of the superconducting state around 7.0 GPa. X-ray diffraction and M\"ossbauer studies explain this fact by a tetragonal-to-hexagonal structural phase transition. M\"ossbauer parameters of the non-superconducting high-pressure phase indicate less covalency of Fe-Se bonds. Based on structural and susceptibility data we conclude about a common character of Tc(p) diagrams for both FeSe and FeSe0.5Te0.5 superconductors.