Pressure-induced isostructural phase transition and correlation of FeAs coordination with the superconducting properties of 111-type Na1-xFeAs

TL;DR

This study investigates how pressure affects the crystal structure and superconducting temperature of Na1-xFeAs, revealing a pressure-induced phase transition and correlations between structure and superconductivity.

Contribution

It provides detailed insights into the pressure-induced structural changes and their correlation with superconducting properties in 111-type Na1-xFeAs.

Findings

Identified a pressure-induced tetragonal to tetragonal isostructural phase transition.

Discovered non-monotonic Tc behavior correlated with structural anomalies.

Observed a second structural phase transition at 20 GPa.

Abstract

The effect of pressure on the crystalline structure and superconducting transition temperature (Tc) of the 111-type Na1-xFeAs system using in situ high pressure synchrotron x-ray powder diffraction and diamond anvil cell techniques is studied. A pressure-induced tetragonal to tetragonal isostructural phase transition was found. The systematic evolution of the FeAs4 tetrahedron as a function of pressure based on Rietveld refinements on the powder x-ray diffraction patterns was obtained. The non-monotonic Tc(P) behavior of Na1-xFeAs is found to correlate with the anomalies of the distance between the anion (As) and the iron layer as well as the bond angle between As-Fe-As for the two tetragonal phases. This behavior provides the key structural information in understanding the origin of the pressure dependence of Tc for 111-type iron pnictide superconductors. A pressure-induced structural phase transition is also observed at 20 GPa.