Possible re-entrant superconductivity in EuFe2As2 under pressure

TL;DR

This study investigates how applying pressure affects EuFe2As2, revealing a possible re-entrant superconductivity phenomenon where superconductivity appears and then reverts as temperature changes.

Contribution

The paper reports the discovery of pressure-induced superconductivity and re-entrant behavior in EuFe2As2, a novel observation in this material under high pressure.

Findings

Superconductivity appears at around 2 GPa with T_c approximately 29.5 K.

Resistivity shows re-entrant behavior related to Eu 2+ magnetic ordering.

The antiferromagnetic transition of FeAs layers is suppressed with pressure.

Abstract

We studied the temperature-pressure phase diagram of EuFe2As2 by measurements of the electrical resistivity. The antiferromagnetic spin-density-wave transition at T_0 associated with the FeAs-layers is continuously suppressed with increasing pressure, while the antiferromagnetic ordering temperature of the Eu 2+ moments seems to be nearly pressure independent up to 2.6 GPa. Above 2 GPa a sharp drop of the resistivity, \rho(T), indicates the onset of superconductivity at T_c \approx 29.5 K. Surprisingly, on further reducing the temperature \rho(T) is increasing again and exhibiting a maximum caused by the ordering of the Eu 2+ moments, a behavior which is reminiscent of re-entrant superconductivity as it is observed in the ternary Chevrel phases or in the rare-earth nickel borocarbides.