1Beijing National Research Center for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China 3Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, College of Physics and Energy, Fujian Normal University, Fuzhou 350117, China 4Songshan Lake Materials Laboratory, Dongguan 523808, China
Abstract：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 ${\boldsymbol{k} \cdot {\boldsymbol p}}$ effective model. The tilted gapless Dirac cones, which are composed of Ta $d$ and C $p$ orbitals and are protected by $C_{4v}$ 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 $\sim$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.
Zhang J L, Zhang S J, Weng H M, Zhang W, Yang L X, Liu Q Q, Feng S M, Wang X C, Yu R C, Cao L Z, Wang L, Yang W G, Liu H Z, Zhao W Y, Zhang S C, Dai X, Fang Z and Jin C Q 2011 Proc. Natl. Acad. Sci. USA108 24
Qian Y, Nie S, Yi C, Kong L, Fang C, Qian T, Ding H, Shi Y, Wang Z, Weng H and Fang Z 2019 npj Comput. Mater.5 121
[8]
Jia Y T, Zhao J F, Zhang S J, Yu S, Dai G Y, Li W M, Duan L, Zhao G Q, Wang X C, Zheng X, Liu Q Q, Long Y W, Li Z, Li X D, Weng H M, Yu R Z, Yu R C and Jin C Q 2019 Chin. Phys. Lett.36 087401
Wang H, Wang H, Liu H, Lu H, Yang W, Jia S, Liu X J, Xie X C, Wei J and Wang J 2016 Nat. Mater.15 38
[18]
Schoop L M, Xie L S, Chen R, Gibson Q D, Lapidus S H, Kimchi I, Hirschberger M, Haldolaarachchige N, Ali M N, Belvin C A, Liang T, Neaton J B, Ong N P, Vishwanath A and Cava R J 2015 Phys. Rev. B91 214517
[19]
Wang D, Kong L, Fan P, Chen H, Zhu S, Liu W, Cao L, Sun Y, Du S, Schneeloch J, Zhong R, Gu G, Fu L, Ding H and Gao H J 2018 Science362 333
[20]
Machida T, Sun Y, Pyon S, Takeda S, Kohsaka Y, Hanaguri T, Sasagawa T and Tamegai T 2019 Nat. Mater.18 811
[21]
Liu Q, Chen C, Zhang T, Peng R, Yan Y J, Wen C H P, Lou X, Huang Y L, Tian J P, Dong X L, Wang G W, Bao W C, Wang Q H, Yin Z P, Zhao Z X and Feng D L 2018 Phys. Rev. X8 041056
Giannozzi P, Baroni S, Bonini N, Calandra M, Car R, Cavazzoni C, Ceresoli D, Chiarotti G L, Cococcioni M, Dabo I, Dal Corso A, de Gironcoli S, Fabris S, Fratesi G, Gebauer R, Gerstmann U, Gougoussis C, Kokalj A, Lazzeri M, Martin-Samos L, Marzari N, Mauri F, Mazzarello R, Paolini S, Pasquarello A, Paulatto L, Sbraccia C, Scandolo S, Sclauzero G, Seitsonen A P, Smogunov A, Umari P and Wentzcovitch R M 2009 J. Phys.: Condens. Matter21 395502
2020, Vol. 37 
