Evidence for conventional superconductivity in Bi2PdPt and prediction of possible 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 (SR) 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 BiPdₓPt_1-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 nontrivial topological state when $x>0.75$ and a trivial topological state when $x<0.75$. Therefore our results indicate that BiPdₓPt_1-x could be a topological superconductor for $x>0.75$.