Discovery of topological surface states in PdTe₂ electronic structure

Jhih-Wei Chen^1*, 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, email:chen.jw@nsrrc.org.tw

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)