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. The coexistence of superconductivity and type-II Dirac points in PdTe2 makes it significantly, which could provide a possible platform to explore the interplay between superconducting quasiparticles and Dirac fermions.
Recently, the research group of Functional Materials Laboratory at Institute of Solid State Physics, Hefei Institutes of Physical Science found that external pressure can manipulate the type-I and type-II Dirac points in PdTe2.
The research group studied the evolution of Dirac cones in PdTe2 under hydrostatic pressure by first-principles calculations.
They found 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¨C6.1 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 ¦£ and A points, which have antibonding/bonding characters of the interlayer Te-Te atoms.
On the other hand, the group found 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.
Figure 1 Evolution of the Dirac points of PdTe2 from 0 to 10 GPa and 3D band structures at 5 GPa. (Image by XIAO Ruichun)
Figure 2. Band and k composed charge density near the Dirac point. The appear of type-I Dirac points and disappear of type-II Dirac points attribute to the shifting upward and downwoard of the corresponding states at ¦£ and A points. (Image by XIAO Ruichun)
The present work was published on Physical Review B entitled ¡°Manipulation of type-I and type-II Dirac points in PdTe2 superconductor by external pressure¡±. The research works were financed by National Key Research and Development Program and National Natural Science Foundation of China.
Prof. SUN Yuping
Institute of Solid State Physics, Chinese Academy of Sciences
High Magnetic Field Laboratory, Chinese Academy of Sciences
Hefei, Anhui 230031, China