High temperature superconductivity (Tc onset at 34K) in the high pressure orthorhombic phase of FeSe

TL;DR

This study investigates how applying high pressure to FeSe induces a structural phase transition to an orthorhombic phase with enhanced superconductivity, reaching a Tc of 34K at 22GPa.

Contribution

It reports the discovery of a high-pressure orthorhombic phase in FeSe with significantly increased Tc, expanding understanding of pressure-induced superconductivity in Fe-based materials.

Findings

Superconductivity in FeSe reaches 34K at 22GPa.

A phase transition from tetragonal to orthorhombic occurs at 12GPa.

The tetragonal phase has a bulk modulus of 28.5 GPa.

Abstract

We have studied the structural and superconducting properties of tetragonal FeSe under pressures up to 26GPa using synchrotron radiation and diamond anvil cells. The bulk modulus of the tetragonal phase is 28.5(3)GPa, much smaller than the rest of Fe based superconductors. At 12GPa we observe a phase transition from the tetragonal to an orthorhombic symmetry. The high pressure orthorhombic phase has a higher Tc reaching 34K at 22GPa.