Evidence for conventional superconductivity in Bi₂PdPt and prediction of topological superconductivity in disorder-free γ-BiPd

We present comprehensive investigations into the structural, superconducting, and topological properties of Bi₂PdPt. Magnetization and heat capacity measurements performed on polycrystalline Bi₂PdPt demonstrate a superconducting transition at ≈ 0.8 K. Moreover, muon spin relaxation/rotation (μSR) measurements present evidence for a time reversal symmetry preserving, isotropically gapped superconducting state in Bi₂PdPt. We have also performed density-functional theory (DFT) calculations on Bi₂PdPt alongside the more general isostructural systems, BiPdₓPt₁₋ₓ, of which Bi₂PdPt and γ-BiPd are special cases for $x=0.5$ and $x=1$ respectively. We have calculated the Z₂ topological index from our DFT calculations for a range of substitution fractions, x, between $x=0$ and $x=1$ characterizing the topology of the band structure. We find a non-trivial topological state when $x>0.75$ and a trivial topological state when $x<0.75$. Therefore our results indicate that BiPdₓPt₁₋ₓ could be a topological superconductor for $x>0.75$.