Superconductivity in W3Re2C with chiral structure

TL;DR

This work reports superconductivity in the chiral, noncentrosymmetric compound W$_3$Re$_2$C with a bulk Tc around 6.2 K. Through combined experiments and first-principles calculations, it identifies W$_3$Re$_2$C as a type-II BCS superconductor with an isotropic full gap, where electron-phonon coupling arises mainly from W/Re 5d states interacting with low-frequency phonons. Ab initio results predict a strong EPC (λ ≈ 1.27) and a theoretical Tc near 10.3 K in the absence of SOC, with real-world Tc limited by SOC, grain boundaries, and carbon vacancies; the material also hosts 18 pairs of Weyl points near EF, indicating coexisting superconductivity and Weyl topology. Overall, W$_3$Re$_2$C provides a versatile platform to study the interplay between chiral lattice structure, conventional superconductivity, and topological band features, with potential routes toward topological superconductivity depending on pairing symmetry.

Abstract

We discover superconductivity in cubic W3Re2C with chiral structure and the superconducting transition temperature Tc is about 6.2 K. Detailed characterizations and analysis indicate that W3Re2C is a bulk type-II BCS superconductor with full isotropic gap. Moreover, first-principles calculations indicate that the electron-phonon coupling primarily arises from interactions between W/Re 5d electronic states and their low-frequency phonons. Furthermore, the breaking of inversion symmetry in W3Re2C facilitates the emergence of Weyl points in the electronic structure. Therefore, W3Re2C can serve as a promising platform for investigating the influences of chiral structure on both superconductivity and band topology.

Figures (5)

• Figure 1: (a) Crystal structure of W$_{3}$Re$_{2}$C. W, Re, and C is represented by medium orange, big red, and small black balls, respectively. (b) PXRD pattern and Rietveld refinement of W$_{3}$Re$_{2}$C. (c) Temperature dependence of $\rho(T)$ at zero field for W$_{3}$Re$_{2}$C polycrystal. Inset: enlarged view of $\rho(T)$ curve below 10 K. (d) Temperature dependence of 4$\pi\chi(T)$ for W$_{3}$Re$_{2}$C measured in the magnetic field of 1 mT with ZFC and FC modes. Inset: isothermal magnetization loops at $T$ = 1.8 K.
• Figure 2: (a) $\rho(T)$ as a function of temperature at various magnetic fields up to 9 T. (b) Temperature dependence of $\mu_{0}H_{c2}(T)$. The green line represents the fit using the WHH formula. (c) Low-field parts of 4$\pi M(\mu_{0}H)$ curves at various temperatures below $T_{c}$. The red line is the Meissner line. (d) Temperature dependence of $\mu_{0}H_{c1}(T)$. The red line is the fit using the formula $\mu_{0}H_{c1}(T) = \mu_{0}H_{c1}(0)[1 - (T/T_{c})^{2}]$.
• Figure 3: (a) Temperature dependence of $C_{p}/T$ below 7 K at various fields up to 9 T. (b) Low-temperature specific heat $C_{p}/T$ vs. $T^{2}$ at 9 T. The red solid line represents the fit using the formula $C_{p}(T)/T = \gamma + \beta T^{2}$. Inset shows the zero-field $C_{p}(T)$ curve measured from 2 K to 250 K. (c) Electronic specific heat $C_{e}$ as a function of $T$ at zero field. The red solid line is the fit using BCS formula. (d) Field dependence of $\gamma$ from 0 T to 5 T. The linear fit is shown as blue solid line.
• Figure 4: Electronic band structure with orbital weights and PDOS of W$_{3}$Re$_{2}$C. (b) Side and top views of FS sheets with the projection of Fermi velocity. The high symmetry k points are labeled by red dots. (c) Phonon dispersion weighted by the EPC strength $\lambda_{\textbf{q}\nu}$. (d) Eliashberg spectral function $\alpha^2F(\omega)$, frequency-dependent EPC constant $\lambda(\omega)$, and PHDOS.
• Figure 5: (a) Band structure of W$_{3}$Re$_{2}$C calculated with SOC effect. The red line denotes band 133, which is set as the valence band maximum in the Weyl points calculation. (b) Weyl points plotted in the whole BZ, where red and blue dots possess the topological charge of +1 and –1, respectively. (c) Surface energy bands of W$_{3}$Re$_{2}$C along the high-symmetry paths of projected two-dimensional BZ for the (100) surface terminated by W atoms. (d) Surface spectra of the (100) surface of W$_{3}$Re$_{2}$C at a fixed energy of $E_{\rm F}$ + 20 meV.