A. Santacesarea, C. Filesi, J. Lorenzana

Dip. di Fisica, Sapienza e Istituto dei Sistemi Complessi, ISC-CNR, Italy.

Recent experiments have established superconductivity in the Weyl semimetal PtBi₂ confined to topological surface states with symmetry-enforced nodes located at the centres of the surface Fermi arcs. Motivated by these findings, we develop a phenomenological model for superconductivity on the spin-textured Fermi arcs, tailored to the surface electronic structure of PtBi₂. We show that one can describe the superconducting state with a simpler order parameter than the previously proposed i-symmetry state [Changdar et al., Nature 647, 613 (2025)]. A phenomenologically introduced interaction reproduces the nodal structure. The phase diagram of the model presents regions where the presence of the arcs favours superconductivity with respect to having the same interaction in a Fermi surface without arcs. Inclusion of the spin texture quantitatively modifies the pairing kernel but does not alter the symmetry selection. Our results provide a microscopic underpinning for nodal surface superconductivity in PtBi₂ and clarify how interactions and topology conspire to stabilise high-angular-momentum pairing on Fermi arcs.