Dirac fermions in the layered titanium-based oxypnictide superconductor BaTi2Bi2O

Abstract

First-principles calculations and effective model analysis are used to prove the existence of a single pair of three-dimensional Dirac points in the well-known layered titanium-based oxypnictide superconductor ${\mathrm{BaTi}}_{2}{\mathrm{Bi}}_{2}\mathrm{O}$. The nontrivial topological character of ${\mathrm{BaTi}}_{2}{\mathrm{Bi}}_{2}\mathrm{O}$ is demonstrated by calculating the surface states. The Dirac points, residing on the rotational axis, are found approximately 70 meV below the Fermi level which can be lifted to Fermi surface by Sb doping. The Dirac points and related physics are expected to be detected by angle-resolved photoemission spectroscopy. This compound is also found to be a superconductor with transition temperature $({T}_{c})4$.6 K; our results may provide an appropriate platform to study the interplay between topological Dirac fermions and superconductivity.