Quantum oscillations and a non-trivial Berry phase in the noncentrosymmetric topological superconductor candidate BiPd

The search for topological superconductors (TSCs) is now at the forefront of condensed matter problems. TSCs are characterized by a full superconducting gap in the bulk and topologically protected gapless surface or edge states at the surface, which are Andreeb bound states made of Majorana fermionic modes. In general the topological systems are investigated through their electronic structures via quantum oscillations. We report the measurements of the de Haas-van Alphen (dHvA) oscillations in the noncentrosymmetric superconductor BiPd. Several pieces of a complex multi-sheet Fermi surface have been identified. Among those, a 40 T pocket was found to be three dimensional and anisotropic in nature. From the temperature dependence of the amplitude of the oscillations, the cyclotron effective mass is (0.18 ± 0.1)m_e. Further analysis showed a non-trivial π-Berry phase is associated with the 40 T pocket, which strongly supports the presence of topological states in the interior of BiPd and may result in topological superconductivity due to proximity effect and or band coupling.