Superconductivity in Bismuth Pyrochlore Lattice Compounds RbBi₂ and CsBi₂: The Role of Relativistic Effects

Superconducting properties of two bismuthide intermetalliccompounds,RbBi2 and CsBi2, were studied by means of experimentalmeasurements and ab initio calculations. We showthat in both compounds, the superconductivity emerges from the pyrochloreBi lattice and its formation is heavily influenced by relativisticeffects. Based on our analysis of the effect of spin-orbitcoupling on the electron-phonon coupling, we suggest a possiblecriterion for finding new superconducting materials by looking forstructures featuring relativistically stabilized hypervalent networksof heavy p-block elements.