Superconductivity in the medium entropy alloys Nb2TiW and Nb2TiMo

TL;DR

This paper reports the synthesis and detailed characterization of Nb2TiW and Nb2TiMo medium entropy alloys, revealing their superconducting properties and confirming their BCS s-wave superconductivity with specific transition temperatures.

Contribution

It introduces the successful synthesis and comprehensive analysis of Nb2TiW and Nb2TiMo MEAs, highlighting their superconducting characteristics and electronic structure.

Findings

Nb2TiW has a Tc of ~4.86 K

Nb2TiMo has a Tc of ~3.22 K

Both alloys exhibit BCS full-gap s-wave superconductivity

Abstract

This study describes the synthesis and characterization of Nb2TiW and Nb2TiMo medium entropy alloys (MEAs). The Nb2TiW and Nb2TiMo MEAs can be successfully synthesized by an arc melting method. Their structures and superconducting properties are investigated by detailed characterization of X ray diffraction (XRD), resistivity, magnetization, and specific heat measurements. XRD results confirm that the obtained Nb2TiW and Nb2TiMo compounds have the same body-centered cubic (BCC) structures. Experimental results show that the superconducting transition temperatures Tcs of Nb2TiW and Nb2TiMo are around 4.86 K and 3.22 K, respectively. The upper and lower critical fields of Nb2TiW are 3.52(2) T and 53.36(2) Oe, respectively, and those of Nb2TiMo are 2.11(2) T and 68.23(3) Oe, respectively. First-principles calculations reveal that the d electrons of Nb, Ti, and Mo or W are the dominant contribution of the density of states near the Fermi level. Specific heat measurement results indicate that Nb2TiW and Nb2TiMo display BCS full-gap s-wave superconductivity.