About the Pressure-Induced Superconducting State of Europium Metal at Low Temperatures

TL;DR

This paper critically examines previous claims of superconductivity in europium under high pressure, highlighting the need for further experiments to confirm or refute earlier findings.

Contribution

It provides new experimental insights questioning the validity of earlier reports on Eu's superconductivity under pressure.

Findings

Previous Eu superconductivity claims are uncertain.

Recent measurements cast doubt on earlier results.

Further experiments are necessary for confirmation.

Abstract

In Phys. Rev. Lett. 102, 197002 (2009) it was reported that the element Eu becomes superconducting in the pressure and temperature range [84-142GPa], [1.8-2.75K]. The claim was largely based on ac susceptibility measurements. Recently reported ac susceptibility measurements on a hydride compound under pressure that appears to become superconducting near room temperature (Nature 586, 373 (2020)) cast serious doubt on the validity of the results for Eu as well as for the hydride. Here I present results that shed new light on the true behaviour of Eu. It is argued that the experiments on Eu have to be repeated to either validate or rule out the claim that it is a superconducting element.