Sudden reversal in the pressure dependence of Tc in the iron-based superconductor CsFe2As2: A possible link between inelastic scattering and pairing symmetry

We report a sudden reversal in the pressure dependence of Tc in the iron-based superconductor CsFe2As2, similar to that discovered recently in KFe2As2 [Tafti , Nat. Phys. 9, 349 (2013)10.1038/nphys2617]. As in KFe2As2, we observe no change in the Hall coefficient at T→0, again ruling out a Lifshitz transition across the critical pressure Pc. We interpret the Tc reversal in the two materials as a phase transition from one pairing state to …