Intrinsic Properties of AFe2As2 (A = Ba, Sr) Single Crystal under Highly Hydrostatic Pressure Conditions

TL;DR

This study investigates how pressure affects the magnetic, structural, and superconducting properties of BaFe2As2 and SrFe2As2 single crystals, revealing a pressure-induced superconducting dome in SrFe2As2.

Contribution

It provides detailed high-pressure measurements of AFe2As2 crystals, highlighting the different behaviors of Ba and Sr compounds and identifying the pressure range for superconductivity in SrFe2As2.

Findings

AF and structural transitions in BaFe2As2 persist up to 8 GPa without superconductivity.

SrFe2As2 exhibits collapse of AF and structural transitions at ~5 GPa, leading to bulk superconductivity.

Superconductivity in SrFe2As2 forms a dome centered around 6 GPa, competing with the AF/orthorhombic phase.

Abstract

We measured the electrical resistivity and ac magnetic susceptibility of BaFe2As2 and SrFe2As2 single crystals under pressure using a cubic anvil apparatus. For BaFe2As2, the antiferromagnetic (AF) and structural transitions are suppressed with increasing pressure. Unexpectedly, these transitions persist up to 8 GPa, and no signature of a superconducting transition was observed in the pressure range investigated here. On the other hand, the AF and structural transitions of SrFe2As2 collapse at around the critical pressure Pc ~ 5 GPa, resulting in the appearance of bulk superconductivity. The superconducting volume fraction abruptly increases above Pc, and shows a dome centered at approximately 6 GPa. Our results suggest that the bulk superconducting phase competes with the AF/orthorhombic phase and only appears in the narrow pressure region of the tetragonal phase.