Pressure-induced superconductivity in Eu$_{0.5}$Ca$_{0.5}$Fe$_2$As$_2$ : FeAs-based superconductivity hidden by antiferromagnetism of Eu sublattice

TL;DR

This study demonstrates that applying high pressure to Eu0.5Ca0.5Fe2As2 induces superconductivity around 20-24 K, revealing hidden superconductivity suppressed by Eu antiferromagnetism, similar to other AFe2As2 compounds.

Contribution

The paper shows pressure-induced superconductivity in Eu0.5Ca0.5Fe2As2, highlighting the suppression of Eu antiferromagnetism as a pathway to reveal FeAs-based superconductivity.

Findings

Superconductivity appears above 1.27 GPa with Tc around 20 K.

Maximum Tc of 24 K at 2.14 GPa with sharp transition.

Superconductivity emergence is similar to other AFe2As2 compounds.

Abstract

To clarify superconductivity in EuFe2As2 hidden by antiferromagnetism of Eu2+, we investigated a Ca-substituted sample, Eu0.5Ca0.5Fe2As2, under high pressure. For ambient pressure, the sample exhibits a spin-density-wave (SDW) transition at TSDW = 191 K and antiferromagnetic order at TN = 4 K, but no evidence of superconductivity down to 2 K. The Ca-substitution certainly weakens the antiferromagnetism. With increasing pressure, TSDW shifts to lower temperature and becomes more unclear. Above 1.27 GPa, pressure-induced superconductivity with zero resistivity is observed at around Tc = 20 K. At 2.14 GPa, Tc reaches a maximum value of 24 K and the superconducting transition becomes the sharpest. These features of emergence of the superconductivity are qualitatively similar to those observed in AFe2As2 (A = Ba, Ca).