The suppression of magnetism and the development of superconductivity within the collapsed tetragonal phase of Ca0.67Sr0.33Fe2As2 at high pressure

TL;DR

This study investigates how high pressure induces a structural phase transition in (Ca0.67Sr0.33)Fe2As2, suppresses magnetism, and promotes superconductivity with a maximum Tc of 22.2 K, revealing the interplay between structure, magnetism, and superconductivity.

Contribution

It provides detailed pressure-dependent structural and electronic data on (Ca0.67Sr0.33)Fe2As2, highlighting the role of volume collapse and magnetic suppression in superconductivity development.

Findings

Pressure induces a volume collapse associated with As-As bonding.

Superconductivity emerges with Tc up to 22.2 K after magnetism suppression.

Maximum Tc is not strongly linked to structural parameters but related to magnetic suppression.

Abstract

Structural and electronic characterization of (Ca0.67Sr0.33)Fe2As2 has been performed as a func- tion of pressure up to 12 GPa using conventional and designer diamond anvil cells. The compound (Ca0.67Sr0.33)Fe2As2 behaves intermediate between its end members-CaFe2As2 and SrFe2As2- displaying a suppression of magnetism and the onset of superconductivity. Like other members of the AEFe2As2 family, (Ca0.67Sr0.33)Fe2As2 undergoes a pressure-induced isostructural volume collapse, which we associate with the development of As-As bonding across the mirror plane of the structure. This collapsed tetragonal phase abruptly cuts off the magnetic state, giving rise to superconductivity with a maximum Tc=22.2 K. The maximum Tc of the superconducting phase is not strongly correlated with any structural parameter, but its proximity to the abrupt suppression of magnetism as well as the volume collapse transition suggests that magnetic interactions and structural inhomogeneity may play a role in its development. The pressure-dependent evolution of the ordered states and crystal structures in (Ca,Sr)Fe2As2 provides an avenue to understand the generic behavior of the other members of the AEFe2As2 family.