Transport signatures of the topological surface state induced by the size effect in superconductor β-PdBi2

The superconductivity and nontrivial topological electronic state are key hallmarks of topological superconductors. Here, we focus on the transport signals of possible topological surface state in the topological superconductor candidate beta-PdBi2 nanoflake with a thickness of 21 nm. The resistance demonstrates a semiconductor-metal transition followed by an upturned behavior as the temperature decreases. A large and unsaturated longitudinal magnetoresistance (MR), accompanied by distinct Shubnikov-de Hass oscillation in Hall resistance, is observed. An analysis of Hall resistance reveals that the carriers present the characteristics of relativistic particles with small effective mass and extremely high mobility. The angle-dependent quantum oscillations demonstrate a two-dimensional Fermi surface topology. A giant anisotropic MR as large as 98% is detected when rotating the magnetic field. These results provide the possible transport signals of a nontrivial topological electronic state, establishing a further understanding of the topological properties of the low-dimensional topological superconductor candidate alpha-PdBi2.

Automated summary

In this study, the possible transport signals of topological surface states in a 21nm thick beta-PdBi2 nanoflake were investigated. The resistance showed a semiconductor-metal transition followed by an upturned behavior as the temperature decreased. The observed large and unsaturated longitudinal magnetoresistance and Shubnikov-de Hass oscillation in Hall resistance suggested the presence of carriers with characteristics of relativistic particles. Angle-dependent quantum oscillations indicated a two-dimensional Fermi surface topology. A giant anisotropic magnetoresistance as high as 98% was detected when rotating the magnetic field. These findings provide valuable insights into the topological properties of the low-dimensional topological superconductor candidate alpha-PdBi2.