Complete pressure dependent phase diagrams for SrFe2As2 and BaFe2As2

TL;DR

This study maps the pressure-dependent phase diagrams of SrFe2As2 and BaFe2As2, revealing how pressure suppresses magnetic order and induces superconductivity, with evidence of quantum critical behavior near the critical pressure.

Contribution

It provides complete pressure-dependent phase diagrams for SrFe2As2 and BaFe2As2, elucidating the relationship between magnetic, structural, and superconducting phases under high pressure.

Findings

Suppression of magnetic/structural transition with pressure

Emergence of superconductivity near critical pressure

Evidence of quantum criticality in resistivity behavior

Abstract

The temperature dependent electrical resistivity of single crystalline SrFe2As2 and BaFe2As2 has been measured in a liquid medium, modified Bridgman anvil cell for pressures in excess of 75 kbar. These data allow for the determination of the pressure dependence of the higher temperature, structural / antiferromagnetic phase transitions as well as the lower temperature superconducting phase transition. For both compounds the ambient pressure, higher temperature structural / antiferromagnetic phase transition can be fully suppressed with a dome-like region of zero resistivity found to be centered about its critical pressure. Indeed, qualitatively, the temperature dependence of the resistivity curves closest to the critical pressures are the closest to linear, consistent with possible quantum criticality. For pressures significantly higher than the critical pressure the zero resistivity state is suppressed and the low temperature resistivity curves asymptotically approach a universal, low temperature manifold. These results are consistent with the hypothesis that correlations / fluctuations associated with the ambient-pressure, high-temperature, tetragonal phase have to be brought to low enough temperature to allow superconductivity, but if too fully suppressed can lead to the loss of the superconducting state.