Figure 3: ARPES spectra along the Fermi surface for representative dopings.

Samples are labelled by a doping-level prefix, namely underdoped (UD), optimum (OP) or overdoped (OD), and a trailing number denoting T_c. (a–d) Energy-versus-sin2θ plots of the spectral images for BB, taken in the superconducting state at T=10 K and symmetrized with respect to ω=0 and θ=0. Circles, curves and blue lines denote the gap energies, the next-higher-harmonic fits and the nodal tangents, respectively. (e–h) EDCs at the momenta marked by triangles in panels a–d. Black curves and vertical bars denote the fits and the gap energies, respectively. (i) EDCs in the normal state at T=80 K for UD66 (see Supplementary Fig. S2 for other dopings). (j) Gap energies as functions of sin2θ in the superconducting (red) and normal (green) states of UD66, determining the energies of antinodal gap Δ^*, nodal gap Δ_N and arc-endpoint gap Δ_arc (see Supplementary Fig. S2 for other dopings). Error bars indicate the uncertainty of EDC fit. The inset shows the doping dependence of the Fermi-arc endpoint, θ_arc, at TT_c+10 K alongside θ_arc/p=100^° (dotted line). The error bars of θ_arc stem from the natural broadness of the EDC peaks. The angles inside and outside θ_arc are labelled by bold and italic faces in e–i, and marked by filled and open triangles in a–d, respectively.