The exploration of topological Dirac semimetals with intrinsic superconductivity can be a most plausible way to discover topological superconductors. We propose that type-II Dirac semimetal states exist in the band structure of TaC, a well-known s-wave superconductor, by using the first-principles calculations and the k ⋅ p effective model. The tilted gapless Dirac cones, which are composed of Ta d and C p orbitals and are protected by C 4 v symmetry, are found to be below the Fermi level. The bands from Ta d orbitals are greatly coupled with the acoustic modes around the zone boundary, indicating their significant contribution to the superconductivity. The relatively high transition temperature ∼10.5 K is estimated to be consistent with the experimental data. To bring the type-II Dirac points close to chemical potential, hole doping is needed. This seems to decrease the transition temperature a lot, m...

中文翻译：

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超导体碳化钽中的II型Dirac半金属态

具有固有超导性的拓扑狄拉克半金属的探索可能是发现拓扑超导体的最合理的方法。通过使用第一性原理计算和k⋅p有效模型，我们建议在著名的s波超导体TaC的能带结构中存在II型狄拉克半金属态。发现由Ta d和C p轨道组成并受C 4 v对称性保护的倾斜无间隙Dirac锥低于费米能级。Ta d轨道的频带与区域边界周围的声模极大地耦合，表明它们对超导性有重大贡献。估计较高的转变温度〜10.5 K与实验数据一致。为了使II型Dirac点接近化学势，需要进行空穴掺杂。