Topological character of A15 superconductors

A15 superconductors are type-II s-wave BCS superconductors that have been known for decades. However, the topological aspects of their electronic structures remain unnoticed so far. In this study, we perform first-principles band structure calculations to show that the band topology of the A15 superconductors Ta₃Sb, Ta₃Sn, and Ta₃Pb is nontrivial. We also find that there appear topological surface states in accordance with the bulk-boundary correspondence. Due to the bulk superconductivity and the proximity effect, topological superconductivity will be induced at the surface, which can host Majorana zero modes at vortices. Our results show that the A15 superconductors are promising candidate materials to realize the p_x + i p_y type topological superconductivity and the Majorana mode.