Manipulation of type-I and type-II Dirac points in PdTe2 superconductor by external pressure

A pair of type-II Dirac cones in PdTe2 was recently predicted by theories and confirmed in experiments, making PdTe2 the first material that processes both superconductivity and type-II Dirac fermions. In this paper, we study the evolution of Dirac cones in PdTe2 under hydrostatic pressure by first-principles calculations. Our results show that the pair of type-II Dirac points disappears at 6.1 GPa. Interestingly, a new pair of type-I Dirac points from the same two bands emerges at 4.7 GPa. Due to the distinctive band structures compared with those of PtSe2 and PtTe2, the two types of Dirac points can coexist in PdTe2 under proper pressure (4.7-6.1 GPa). The emergence of type-I Dirac cones and the disappearance of type-II Dirac ones are attributed to an increase/decrease of the energy of the states at the Gamma and A points, which have antibonding/bonding characters of the interlayer Te-Te atoms. On the other hand, we find that the superconductivity of PdTe2 slightly decreases with pressure. The pressure-induced types of Dirac cones combined with superconductivity may open a promising way to investigate the complex interactions between Dirac fermions and superconducting quasiparticles.