Observation of superconductivity in the pressurized Weyl-semimetal candidate $\mathrm{TaIrT}{\mathrm{e}}_4$

We report the observation of superconductivity in the pressurized type-II Weyl semimetal (WSM) candidate $\mathrm{TaIrT}{\mathrm{e}}_4$ by means of complementary high-pressure transport and synchrotron x-ray diffraction measurements. We find that $\mathrm{TaIrT}{\mathrm{e}}_4$ shows superconductivity with transition temperature $\left(T_C\right)$ of 0.57 K at the pressure of $\sim 23.8\mathrm{GPa}$. Then, the $T_C$ value increases with pressure and reaches $\sim 2.1\mathrm{K}$ at 65.7 GPa. In situ high-pressure Hall coefficient $\left(R_H\right)$ measurements at low temperatures demonstrate that the positive $R_H$ increases with pressure until the critical pressure of the superconducting transition is reached, but starts to decrease upon further increasing pressure. Above the critical pressure, the positive magnetoresistance effect disappears simultaneously. Our high-pressure x-ray diffraction measurements reveal that at around the critical pressure, the lattice of the $\mathrm{TaIrT}{\mathrm{e}}_4$ sample is distorted and its volume is reduced by $\sim 19.2\%$, the value of which is predicted to result in the change of the electronic structure significantly. We propose that the pressure-induced distortion in $\mathrm{TaIrT}{\mathrm{e}}_4$ is responsible for the change of topology of the Fermi surface, and such a change favors the emergence of superconductivity. Our results reveal the correlation among the lattice distortion, topological physics, and superconductivity in the WSM, a hot topic in condensed-matter physics.

Figure 1

Temperature dependence of electrical resistance of $\mathrm{TaIrT}{\mathrm{e}}_4$ at different pressures. (a), (b) Resistance as a function of temperature up to 19.2 GPa for the sample 1 (S#1) and 65.7 GPa for the sample 2 (S#2). (c), (d) The low-temperature resistance of (b), displaying the superconducting transitions at higher pressures. The inset of (d) exhibits the superconducting transition observed from the sample 3 (S#3).

Figure 2

Characterizations of pressure-induced superconductivity in WSM candidate $\mathrm{TaIrT}{\mathrm{e}}_4$. (a) Magnetic field dependence of the superconducting transition temperature measured at 45 GPa. The inset shows upper critical field $H{c}_2$ as a function of superconducting transition temperature $T_C$ for pressurized $\mathrm{TaIrT}{\mathrm{e}}_4$. (b) The results of high-pressure ac susceptibility measurements.

Figure 3

Structural information for pressurized WSM candidate $\mathrm{TaIrT}{\mathrm{e}}_4$. (a) Schematic crystal structure of $\mathrm{TaIrT}{\mathrm{e}}_4$. In the crystallographic description, $\mathrm{TaIrT}{\mathrm{e}}_4$ crystallizes in an orthorhombic unit cell. (b) X-ray diffraction patterns collected at different pressures. (c), (d) Pressure dependence of lattice parameters for the orthorhombic $\mathrm{TaIrT}{\mathrm{e}}_4$ up to 26.9 GPa. (e) Plots of $d$-spacing value vs pressure which are extracted from the high-pressure x-ray diffraction data.

Figure 4

Summary of experimental results of WSM candidate $\mathrm{TaIrT}{\mathrm{e}}_4$. (a) Pressure -$T_C$ phase diagram with structure information for $\mathrm{TaIrT}{\mathrm{e}}_4$. WSM and SC represent Weyl semimetal and superconducting states, respectively. S#2, S#3, and S#4 stand for the sample 2, sample 3, and sample 4 (see data of S#4 in the Supplemental Material [76]). (b) Pressure dependence of Hall coefficient measured at 10 K. (c) Magnetoresistance (MR) as a function of pressure measured at 10 K, where $\mathrm{MR}\%=\left[R\left(7T\right)–R\left(0\right)\right]/R\left(0T\right)\times 100\%$.