Discovery of topological surface states in PdTe2 electronic structure
Jhih-Wei Chen1*, Chia-Nung Kuo2, Wei-Chuan Chen3, Chin-Shan Lue2, Cheng-Maw Cheng1, Chia-Hao Chen1, Tay-Rong Chang2
1NanoScience Group, National Synchrotron Radiation Research Center, HsinChu, Taiwan
2Department of Physics, National Cheng Kung University, Tainan, Taiwan
3Department of Physics, National Tsing Hua University, HsinChu, Taiwan
* Presenter:Jhih-Wei Chen,
The discovery of topological surface state in a new class of materials, particularly in topological superconductor, is of critical importance in realizing new quantum phenomena and further devices. The topological surface state has been predicted and observed mainly in Bi2Se3 and related compounds, but rarely discovered in superconducting transition metal dichalcogenides (TMDs). The TMDs has been a rich playground to discover new material property, but there are very few reports related to the discovery of topological band structures. In this work, we investigate the topological band structure of TMD superconductors, like PdTe2 crystal, by using combined method of angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). We observe a pair of symmetry-protected Dirac point along kz direction, which reveals exotic type II band dispersion that strongly violate Lorentz symmetry. In addition, our DFT calculations predict PdTe2 possesses an unexpected ℤ2 topological invariant and fully spin-polarized Dirac surface states without any doping introducing or external pressure applying. This type of intrinsic topological Dirac superconducting insulator holds a great promise for studying aspects of topological superconductor as well as Majorana zero modes.

Keywords: TMD superconductor, Topological insulator, Angle-resolved photoemission spectroscopy (ARPES), Density functional theory (DFT)