Superconductivity in equimolar Nb-Re-Hf-Zr-Ti high entropy alloy

Abstract

Herein, we report the synthesis and detailed superconducting properties of a new high entropy alloy superconductor with nominal composition Nb${}_{20}$Re${}_{20}$Zr${}_{20}$Hf${}_{20}$Ti${}_{20}$ using powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), magnetization, transport, and thermodynamic measurements. The room temperature powder XRD confirms that the alloy is arranged on a simple body centered cubic crystal lattice with lattice parameter a = 3.38 (1) $\text{A˚}$. EDX measurement yields an average composition of Nb${}_{21}$Re${}_{16}$Zr${}_{20}$Hf${}_{23}$Ti${}_{20}$ (in atomic $\%$). Transport, magnetic and heat capacity measurements reveal that the material is a type-II superconductor with the bulk superconducting transition at $T_c$ = 5.3 K, lower critical field $H_{c1}$(0) = 33 mT and upper critical field $H_{c2}$(0) = 8.88 T. Low temperature specific heat measurement indicates that the sample is a moderately coupled superconductor, and the electronic specific heat data fits well with the single-gap BCS model.

6 Pages, 7 Figures