No abstract

High entropy alloys (HEAs) are the new class of materials with an attractive combination of tunable mechanical and physicochemical properties. They crystallize mainly in cubic structures, however, for practical applications, HEAs with hexagonal close-packed (hcp) structure are highly desirable in connection to their in general high hardness. Herein, we report the synthesis, structure and detailed superconducting properties of Re0.56Nb0.11Ti0.11Zr0.11Hf0.11-the first hexagonal superconducting high entropy alloy (HEA) composed of five randomly distributed transition-metals. Combination of room temperature precession electron diffraction, precession electron diffraction tomography and powder X-ray diffraction is utilized to determine the room temperature crystal structure. Transport, magnetic and heat capacity measurements show that the material is a type-II superconductor with the bulk superconducting transition at Tc = 4.4 K, lower critical field Hc1(0) = 2.3 mT and upper critical field Hc2(0) = 3.6 T. Low-temperature specific heat measurement indicates that Re0.56Nb0.11Ti0.11Zr0.11Hf0.11 is a phonon-mediated superconductor in the weak electron-phonon coupling limit with a normalized specific heat jump ∆C el γnTc = 1.32. Further, hexagonal to cubic structural transition is observed by lowering the valence electron counts and Tc follows crystalline-like behaviour.

This work presents the emergence of superconductivity in Re substituted topological Weyl semimetal MoTe2. Re substitution for Mo sites lead to a sizable enhancement in the superconducting transition temperature (Tc). A record high Tc at ambient pressure in a 1T -MoTe2 (room temperature structure) related sample is observed for the Mo0.7Re0.3Te2 composition (Tc = 4.1 K, in comparison MoTe2, shows a Tc of 0.1 K). The experimental and theoretical studies indicate that Re substitution is doping electrons and facilitates the emergence of superconductivity by enhancing the electronphonon coupling and density of states at the Fermi level. Our findings, therefore, open a new way to further manipulate and enhance the superconducting state together with the topological states in 2D van der Waals materials.