Extremely high sensitivity to uniaxial stress in pressure induced superconductivity of BaFe2As2

TL;DR

This study reveals that tiny uniaxial stress along the c-axis drastically influences the pressure-induced superconductivity in BaFe2As2, showing high sensitivity and phase diagram variability depending on pressure conditions.

Contribution

It demonstrates the extreme sensitivity of BaFe2As2's superconductivity to uniaxial stress, highlighting the importance of pressure hydrostaticity in phase transition studies.

Findings

Superconductivity appears between 11 and 14 GPa under highly hydrostatic pressure.

Small uniaxial stress along c-axis suppresses magnetic order and stabilizes superconductivity at lower pressures.

Phase diagram varies significantly with pressure hydrostaticity.

Abstract

We have performed electrical resistivity measurements on single crystal BaFe2As2 under high pressure P up to 16 GPa with a cubic anvil apparatus, and up to 3 GPa with a modified Bridgman anvil cell. The samples were obtained from the same batch, which was grown with a self-flux method. A cubic anvil apparatus provides highly hydrostatic pressure, and a modified Bridgman anvil cell, which contains liquid pressure transmitting medium, provides quasi hydrostatic pressure. For highly hydrostatic pressure, the crystal phase and magnetic transition temperature decreases robustly with P and disappears at around 10 GPa. The superconducting phase appears adjacent to magnetic phase in narrow pressure region between 11 and 14 GPa. The tiny difference of hydrostaticity between the cubic anvil apparatus and modified Bridgman anvil cell induces a drastic effect on the phase diagram of BaFe2As2. This result indicates that small uniaxial stress along c-axis strongly suppresses the structural/antiferromagnetic ordering and stabilizes superconductivity at much lower pressure.