Important roles of Te 5p and Ir 5d spin-orbit interactions on the multi-band electronic structure of triangular lattice superconductor Ir_1-xPt_xTe₂

We report an angle-resolved photoemission spectroscopy (ARPES) study on a triangular lattice superconductor Ir_1-xPt_xTe₂ in which the Ir-Ir or Te-Te bond formation, the band Jahn-Teller effect, and the spin-orbit interaction are cooperating and competing with one another. The Fermi surfaces of the substituted system are qualitatively similar to the band structure calculations for the undistorted IrTe₂ with an upward chemical potential shift due to electron doping. A combination of the ARPES and the band structure calculations indicates that the Te 5p spin-orbit interaction removes the p_x/p_y orbital degeneracy and induces p_x ± ip_y type spin-orbit coupling near the A point. The inner and outer Fermi surfaces are entangled by the Te 5p and Ir 5d spin-orbit interactions which may provide exotic superconductivity with singlet-triplet mixing.