Topological origin of the type-II Dirac fermions in PtSe2

Journal article

Group VIII transition-metal dichalcogenides have recently been proposed to host type-II Dirac fermions. They are Lorentz-violating quasiparticles marked by a strongly tilted conic dispersion along a certain momentum direction and therefore have no analogs in the standard model. Using high-resolution angle-resolved photoemission spectroscopy, we systematically studied the electronic structure of PtSe2 in the full three-dimensional Brillouin zone. As predicted, a pair of type-II Dirac crossings is experimentally confirmed along the kz axis. Interestingly, we observed conic surface states around time-reversal-invariant momenta Γ and M points. The signatures of nontrivial topology are confirmed by the first-principles calculation, which shows an intricate parity inversion of bulk states. Our discoveries not only contribute to a better understanding of topological band structure in PtSe2 but also help further explore the exotic properties, as well as potential application, of group VIII transition-metal dichalcogenides.

Authors: Li, Y; Xia, Y; Ekahana, S; Kumar, N; Jiang, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Physical Society
• Journal: Physical Review Materials
• Volume: 1
• Issue: 7
• Publication date: 2017-12-22
• Acceptance date: 2017-12-06
• DOI: 10.1103/physrevmaterials.1.074202
• ISSN: 2475-9953
• Language: English
• Keywords: surface states; quasiparticles and collective excitations; topological phases of matterr; condensed matter and materials physics; electronic structure; fermi surface