Figure 4. Momentum dependence of the superconducting gap of (Li_0.84Fe_0.16)OHFe_0.98Se superconductor.

(a) Fermi surface mapping near M2 point. The corresponding Fermi crossings are marked by red empty circles with numbers from 1 to 16 (for clarity, the intermittent points are not labelled). (b) Symmetrized EDCs measured at 20 K from Fermi crossing 1 to 16 along the measured electron-like Fermi surface around M2. The red dashed lines represent the energy positions of ±13 meV with respect to the Fermi level. (c) Momentum dependence of the superconducting gap (red solid circles) along the Fermi surface around M2 for (Li_0.84Fe_0.16)OHFe_0.98Se superconductor. For comparison, the gap along the electron-like Fermi surface around M2 of the superconducting single-layer FeSe film is also plotted (blue empty circles)²⁰. The error bars are defined as s.d.