Superconductivity in the A15-type V3(Os1-2xSixGex) medium-entropy alloys

TL;DR

This study reports the discovery of new A15-type V3(Os1-2xSixGex) medium-entropy alloy superconductors, demonstrating their type-II behavior, increased Tc with reduced Os, and robustness against magnetic fields, expanding superconductor materials.

Contribution

First synthesis and characterization of A15-type V3(Os1-2xSixGex) medium-entropy alloy superconductors with enhanced properties.

Findings

All samples are type-II bulk superconductors.

Superconducting transition temperature increases as Os concentration decreases.

Upper critical field exceeds the Pauli limit, indicating robustness against magnetic fields.

Abstract

Cubic A15-type superconducting alloys continue to fascinate the academic and industrial fields because they mainly support the largest market for low-temperature superconducting applications and show exotic physical properties. Medium-/high-entropy alloys (MEAs-HEAs) can be employed stably under extreme conditions due to their high mechanical hardness and excellent irradiation tolerance. Combining with the features of the A15-type superconductor and MEAs-HEAs, we design a series of previously unreported A15-type V3(Os1-2xSixGex) (x = 0.333, 0.375, 0.425) MEA superconductors, which can be obtained by an arc melting method. Resistivity, magnetic susceptibility, and specific heat measurements indicate that all of them are type-II bulk superconductors. The superconducting transition temperature (Tc) exhibits an upward trend with the systematic reduction of Os concentration. Additionally, the upper critical field of the V3(Os0.333Si0.333Ge0.333) sample is larger than the Pauli limit, suggesting it may be robust against magnetic fields due to spin-orbit coupling induced by the heavy Os atoms. These findings not only advance our understanding of emergent phenomena in entropy-stabilized A15-type alloys but also expand the members of new superconductors.