Determine the superconducting pairing state of FeTe₀.₅Se₀.₅ at high chemical potential

Determine the superconducting pairing state and the precise effective pairing potential of FeTe₀.₅Se₀.₅ at chemical potential μ = 610 meV, where the relevant electronic structure is dominated by a predominantly p-orbital band, in order to establish which topological phase-diagram predictions apply in this regime.

Background

The paper compares topological phase diagrams obtained with momentum-independent s⁺⁺ pairing and sign-changing s± pairing. For transitions associated with Γ- and M-point gap closings, the two pairing choices produce similar results, whereas X- and Y-point transitions are strongly altered by the nodal structure of the s± gap. The authors therefore emphasize that the pairing state and effective pairing potential at μ = 610 meV are essential for interpreting the predicted topological phases.

The unresolved pairing information is particularly important because μ = 610 meV lies near an isolated chalcogen-derived band with substantial p-orbital character, rather than in the more conventional low-energy regime of FeTe₀.₅Se₀.₅. The paper proceeds by analyzing both candidate pairing symmetries, but does not resolve which one—or what precise effective pairing potential—describes this regime.

References

We note, however, that superconductivity in FeTe${0.5}$Se${0.5}$ at $\mu=610$~meV, as well as the precise form of the effective pairing potential in this regime, remains an open question.

— A First-Principles Multiscale Framework for Topological Superconductivity  (2609.10381 - Jacobs et al., 9 Sep 2026) in Section 4, Section “Phase Diagrams and Computation of Chern Number,” subsection “System I: Bulk-like FeTe₀.₅Se₀.₅ on SrTiO₃ substrate”