High-entropy alloys (HEAs) are a 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 with their, in general, high hardness. Herein, we report the synthesis, structure, and detailed superconducting properties of ${\mathrm{Re}}_{0.56}{\mathrm{Nb}}_{0.11}{\mathrm{Ti}}_{0.11}{\mathrm{Zr}}_{0.11}{\mathrm{Hf}}_{0.11}$—the first hexagonal superconducting HEA composed of five randomly distributed transition metals. A 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 $T_c=4.4$ K, lower critical field $H_{c1}\left(0\right)=2.3$ mT, and upper critical field $H_{c2}\left(0\right)=3.6$ T. Low-temperature specific-heat measurement indicates that ${\mathrm{Re}}_{0.56}{\mathrm{Nb}}_{0.11}{\mathrm{Ti}}_{0.11}{\mathrm{Zr}}_{0.11}{\mathrm{Hf}}_{0.11}$ is a phonon-mediated superconductor in the weak electron-phonon coupling limit with a normalized specific-heat jump $\frac{\mathrm{\Delta }{C}_{el}}{{\gamma }_n{T}_c}=1.32$. Further, hexagonal to cubic structural transition is observed by lowering the valence electron counts and $T_c$ follows crystallinelike behavior.

In Weyl semimetals, there is an intriguing possibility of realizing a pseudo-magnetic field in the presence of small strain due to certain special cases of static deformations. This pseudo-magnetic field can be large enough to form quantized Landau levels and thus become observable in Weyl semimetals. In this paper we experimentally show the emergence of a pseudo-magnetic field ($\sim 3$ T) by scanning tunneling spectroscopy on the doped Weyl semimetal Re-${\mathrm{MoTe}}_2$, where distinct Landau-level oscillations in the tunneling conductance are clearly resolved. The crystal lattice is intrinsically strained where large area scanning tunneling microscopy imaging of the surface reveals differently strained domains where atomic scale deformations exist forming topographic ripples with varying periodicity in the real space. The effect of the pseudo-magnetic field is clearly resolved in areas under maximum strain.

This work presents the emergence of superconductivity in Re-substituted topological Weyl semimetal ${\mathrm{MoTe}}_2$. Re substitution for Mo sites leads to a sizable enhancement in the superconducting transition temperature ($T_c$). A record high $T_c$ at ambient pressure in a $1T^{\prime }-{\mathrm{MoTe}}_2$ (room-temperature structure) related sample is observed for the ${\mathrm{Mo}}_{0.7}{\mathrm{Re}}_{0.3}{\mathrm{Te}}_2$ composition ($T_c=4.1\mathrm{K}$; in comparison, ${\mathrm{MoTe}}_2$ shows a $T_c$ 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 electron-phonon 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 two-dimensional van der Waals materials.