Simultaneous measurement of pressure evolution of crystal structure and superconductivity in FeSe0.92 using designer diamonds

TL;DR

This study uses designer diamonds to perform simultaneous high-pressure x-ray diffraction and resistance measurements on FeSe0.92, revealing how its crystal structure and superconductivity evolve under pressures up to 44 GPa.

Contribution

It provides the first simultaneous measurement of structural and superconducting properties of FeSe0.92 under high pressure using designer diamond anvils.

Findings

Superconductivity peaks at ~28 K around 6 GPa.

Structural phase transition from tetragonal to orthorhombic at 11 GPa.

Superconductivity disappears above 14.6 GPa.

Abstract

Simultaneous high pressure x-ray diffraction and electrical resistance measurements have been carried out on a PbO type {\alpha}-FeSe0.92 compound to a pressure of 44 GPa and temperatures down to 4 K using designer diamond anvils at synchrotron source. At ambient temperature, a structural phase transition from a tetragonal (P4/nmm) phase to an orthorhombic (Pbnm) phase is observed at 11 GPa and the Pbnm phase persists up to 74 GPa. The superconducting transition temperature (TC) increases rapidly with pressure reaching a maximum of ~28 K at ~ 6 GPa and decreases at higher pressures, disappearing completely at 14.6 GPa. Simultaneous pressure-dependent x-ray diffraction and resistance measurements at low temperatures show superconductivity only in a low pressure orthorhombic (Cmma) phase of the {\alpha}-FeSe0.92. Upon increasing pressure at 10 K near TC, crystalline phases change from a mixture of orthorhombic (Cmma) and hexagonal (P63/mmc) to a high pressure orthorhombic (Pbnm) phase near 6.4 GPa where TC is maximum.