Normal state and superconducting state properties of high entropy <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Ta</mml:mi> <mml:mrow> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi>Nb</mml:mi> <mml:mrow> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">V</mml:mi> <mml:mrow> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi>Ti</mml:mi> <mml:mrow> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mi>X</mml:mi> <mml:mrow> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>X</mml:mi> <mml:mo>=</mml:mo> <mml:mi>Zr</mml:mi> </mml:mrow> </mml:math> and Hf)

Abstract

High-entropy alloy superconductors represent a unique blend of advanced material systems and quantum physics, offering significant potential for advancing superconducting technologies. In this study, we report a detailed theoretical and experimental investigation of high-entropy alloy superconductors ${\mathrm{Ta}}_{0.2}{\mathrm{Nb}}_{0.2}{\mathrm{V}}_{0.2}{\mathrm{Ti}}_{0.2}{X}_{0.2}$ ($X=\mathrm{Zr}$ and Hf). Our study unveils that both the materials crystallize in a body-centered-cubic structure (space group: Im-3m) and exhibit bulk superconductivity with a superconducting onset temperature of (${T}_{c}^{\text{onset}}$) of 5 K for $X=$ Hf and 6.19 K for $X=\mathrm{Zr}$ sample. Our detailed analysis, including magnetization, resistivity, heat capacity measurements, and density functional $X=\mathrm{Zr}$ theory (DFT) calculations indicates moderately coupled isotropic $s$-wave superconductivity in these materials. Our DFT results find significant spectral weight at the Fermi energy and phonon spectra is free of imaginary modes, confirming the dynamical stability and metallic nature of these alloys. Remarkably, we have observed a high upper critical field $[{H}_{c2}(0)]$ surpassing the Pauli paramagnetic limit for the $X=$ Hf sample and explained it on the basis of the increased spin-orbit coupling in the structure. ${\mathrm{Ta}}_{0.2}{\mathrm{Nb}}_{0.2}{\mathrm{V}}_{0.2}{\mathrm{Ti}}_{0.2}{\mathrm{Zr}}_{0.2}$, on the other hand, shows a conventional ${H}_{c2}$ behavior. With the dynamical stability of these alloys, excellent normal state metallic nature, high microhardness, and high upper critical field, these samples emerge as potential candidates for future applications in superconducting devices.

Topics & Concepts