t-PtBi₂ - Topological Fermi Arcs and Surface Superconductivity

Materials whose electronic properties are governed by exotic quantum phenomena, such as topology and unconventional superconductivity, are at the forefront of current research in the field of condensed matter physics. These materials offer a rich variety of novel unconventional properties, promising to serve as the basis for future low-loss electronics and quantum information processing.

The compound trigonal PtBi₂ (t-PtBi₂) is an intriguing representative of these so-called quantum materials. As a Weyl semimetal candidate, which exhibits sub-Kelvin superconductivity as revealed by transport [1], it potentially combines both a topologically non-trivial electronic structure and superconductivity.

In topological materials, boundaries, such as those given by a surface, play a special role. These can host surface states of topological electrons, e.g. Fermi arcs in case of Weyl semimetals, associated with exotic quasiparticle excitations. The interplay of these surface states with superconductivity raises new fundamental questions and, in particular, research in the field of superconductivity intrinsically intertwined with the existence of topological surface states is still in a nascent state.

Via low-temperature scanning tunneling spectroscopy and quasi-particle interference investigations, we experimentally address the local topological and superconducting properties of the surface of t-PtBi₂. This allows us to uncover its Weyl fermiology as well as superconductivity at elevated temperatures with Tc > 5 K - more than one order of magnitude higher than previously reported by transport. Furthermore, spectroscopic signatures provide clear evidence for the surface nature of superconductivity and suggest the possibility of transition temperatures comparable to those known from high Tc cuprate superconductors. Our results thus experimentally corroborate the non-trivial topology and variable surface superconductivity in t-PtBi₂.

[1] A. Veyrat et al. ACS Nano Lett.(2023)