Exchange field enhanced upper critical field of the superconductivity in compressed antiferromagnetic EuTe2

TL;DR

This study reveals pressure-induced superconductivity in EuTe2, with an exchange field enhancing the upper critical field, and identifies a structural transition affecting magnetic and superconducting properties.

Contribution

It demonstrates the emergence of superconductivity in EuTe2 under high pressure and elucidates the role of exchange fields and structural transitions in its superconducting behavior.

Findings

Superconductivity appears above 5 GPa in EuTe2.

The upper critical field exceeds the Pauli limit in the low-pressure phase.

A structural transition occurs at ~16 GPa, affecting magnetic and superconducting properties.

Abstract

We report high pressure studies on the C-type antiferromagnetic semiconductor EuTe2 up to 36.0 GPa. A structural transition from the I4/mcm to C2/m space group is identified at ~16 GPa. Superconductivity is discovered above ~5 GPa in both the I4/mcm and C2/m space groups. In the low-pressure phase (< 16 GPa), the antiferromagnetic transition temperature is enhanced with increasing pressure due to the enhanced magnetic exchange interactions. Magnetoresistance measurements indicate an interplay between the local moments of Eu2+ and the conduction electrons of Te 5p orbits. The upper critical field of the superconductivity is well above the Pauli limit. Across the structural transition to the high-pressure phase (> 16 GPa), EuTe2 becomes nonmagnetic and the superconducting transition temperature evolves smoothly with the upper critical field below the Pauli limit. Therefore, the high upper critical field of EuTe2 in the low-pressure phase is due to the exchange field compensation effect of the Eu magnetic order and the superconductivity in both structures may arise in the framework of the BCS theory.