Enhancement of the superconducting transition temperature by Re doping in Weyl semimetal ${\mathrm{MoTe}}_2$

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.

Figure 1

Room-temperature crystal structure of the ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$ materials (space group P21/$m, 1T^{\prime }$ phase). The zigzag Mo-Re chains along the $b$ direction are highlighted here.

Figure 2

Room-temperature (RT) powder x-ray diffraction pattern for ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$ samples. Inset shows the unreacted Re peak in the XRD pattern for the $x=0.4$ sample.

Figure 3

Average Re concentration (average of 10 points) obtained from the EDX measurements for ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$ samples.

Figure 4

(a) RT XRD pattern on the cleaved single crystal, (b) the Rietveld refinement plots, (c) EDX pattern, and (d) temperature variation of the magnetic moment for ${\mathrm{Mo}}_{0.9}{\mathrm{Re}}_{0.1}{\mathrm{Te}}_2$ crystals. Images of the grown crystals are shown in the inset of panel (b).

Figure 5

Temperature dependence of (a) resistivity under zero magnetic field for ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$ samples. Solid triangles indicate the structural transition temperatures. Arrows highlight the cooling and heating process. Inset shows the observed anomaly in the normal-state resistivity data for $x=0.1$ and 0.2 samples. (b) Enlarged part of the resistivity measurements highlighting the superconducting transitions for ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$.

Figure 6

Temperature dependence of (a)–(e) dc magnetization and (f) normalized ac susceptibility at a dc magnetic field of 10 Oe (ac excitation field = 2 Oe) for ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$ samples.

Figure 7

Determination of upper critical field $\left[H_{C2}\left(0\right)\right]$ using resistivity measurements. The solid lines represent the Ginzburg–Landau fitting. The upper inset shows the magnetic-field variation of the resistivity for $x=0.4$ sample. The Ginzburg–Landau coherence length for the ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$ materials are shown in the lower inset.

Figure 8

Magnetic-field variation of the Hall resistance at different temperatures for the ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$ samples.

Figure 9

Variation of superconducting transition temperatures ($T_c$, left axis) and magnetoresistance (right axis) with Re substitution level in structure for ${\mathrm{Mo}}_{1-x}{\mathrm{Re}}_x{\mathrm{Te}}_2$.

Figure 10

The low-temperature specific-heat data for ${\mathrm{MoTe}}_2$ and for ${\mathrm{Mo}}_{0.7}{\mathrm{Re}}_{0.3}{\mathrm{Te}}_2$. The specific-heat data above $T_c$ are fit to the Debye model and shown by a solid line.