Dirac Excitations of Bulk and Surface States in PtTe₂ and PdTe₂ probed by Angle-Resolved Photoemission Spectroscopy (ARPES)

Platinum ditelluride (PtTe₂) and palladium ditelluride (PdTe₂) are transitional metal dichalcogenides with excitations that are described by a massless Dirac Hamiltonian. In particular, these materials host type-II Dirac fermions at the bulk with tilted conical energy-momenta dispersions in their electronic band structures i.e., type-II Dirac cones. In addition to the type-II bulk cones, PtTe₂ and PdTe₂ also host topologically protected surface states. To study these bulk and surface states, we performed angle-resolved photoemission spectroscopy (ARPES) on these crystals at the Lawrence Berkeley National Lab using linearly and circularly polarized light. We also superimposed Density Functional theory calculations on our measured data to carefully characterize the electronic band structures and highlight the different symmetries that exist in our crystals. Finally, we differentiated between the bulk and the topologically protected surface states by performing circular dichroism (difference in the intensity photoemission using right- and left- circularly polarized light), showing that even though these states are outcomes of similar symmetries, they are of different nature.