Superconductivity in the bcc-Type High-Entropy Alloy TiHfNbTaMo

Abstract

X-ray powder diffraction, electrical resistivity, magnetization, and thermodynamic measurements are conducted to investigate the structure and superconducting properties of TiHfNbTaMo, a novel high-entropy alloy possessing a valence electron count (VEC) of 4.8. The TiHfNbTaMo HEA is discovered to have a body-centered cubic structure (space group (Formula presented.)) with lattice parameters a = 3.445 (1) Å and a microscopically homogeneous distribution of the constituent elements. This material shows type-II superconductivity with Tc = 3.42 K, lower critical field µ0Hc1(0) = 22.8 mT, and upper critical field µ0Hc2(0) = 3.95 T. Low-temperature specific heat measurements show that the alloy is a conventional s-wave type with a moderately coupled superconductor. First-principles calculations show that the density of states (DOS) of the TiHfNbTaMo alloy is dominated by hybrid d orbitals of these five metal elements. Additionally, the TiHfNbTaMo HEA exhibits three van Hove singularities. Furthermore, the VEC and the composition of the elements (especially the Nb elemental content) affect the Tc of the bcc-type HEA.