Title: Dirac State in a Centrosymmetric Superconductor alpha-PdBi2,
Abstract: Topological superconductor (TSC) hosting Majorana fermions has been
established as a milestone that may shift our scientific trajectory from
research to applications in topological quantum computing. Recently,
superconducting Pd-Bi binaries have attracted great attention as a possible
medium for the TSC phase as a result of their large spin-orbit coupling
strength. Here, we report a systematic high-resolution angle-resolved
photoemission spectroscopy (ARPES) study on the normal state electronic
structure of superconducting alpha-PdBi2 (Tc = 1.7 K). Our results show the
presence of Dirac states at higher-binding energy with the location of the
Dirac point at 1.26 eV below the chemical potential at the zone center.
Furthermore, the ARPES data indicate multiple band crossings at the chemical
potential, consistent with the metallic behavior of alpha-PdBi2. Our detailed
experimental studies are complemented by first-principles calculations, which
reveal the presence of surface Rashba states residing in the vicinity of the
chemical potential. The obtained results provide an opportunity to investigate
the relationship between superconductivity and topology, as well as explore
pathways to possible future platforms for topological quantum computing.