Type-Ⅱ Dirac Semimetal State in a Superconductor Tantalum Carbide

作者：崔志海; 钱玉婷; 张薇^*; 翁红明^*; 方忠

来源：Chinese Physics Letters, 2020, 37(08): 88-92.

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 C4v 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, making the realization of topological superconductivity impossible.

• 单位
  中国科学院大学