Fig. 3: The existence of VHS perfectly aligned with the Fermi level in CsV_2.6Ta_0.4Sb₅.

a Photoelectron intensity plot along Γ-K-M-Γ of CsV_2.6Ta_0.4Sb₅ measured with 21.2 eV photons at 200 K. This photon energy probes the electronic structure in the Γ-K-M plane of the 3D BZ (Supplementary Fig. S2). The red dashed lines are a guide for the eye. b EDCs near M point extracted from the photoemission raw spectrum in the momentum region marked by the blue arrow in (a). c Same as the raw EDCs in (b), but symmetrized to show the absence of an energy gap. d EDCs near M point extracted from the photoemission raw spectrum in the momentum region marked by the yellow arrow in (a). The red triangles and circles in (b), (d) indicate the EDC peaks. e Band dispersion near K and M points (along the Γ-K-M-Γ direction) extracted from the EDC peaks measured at 200 K (red empty circles) and 25 K (magenta solid circles), respectively. f Extracted band dispersion of CsV_2.6Ta_0.4Sb₅ and CsV₃Sb₅ in the momentum region near M, indicated by the black dotted box in (e). The error bars in (e) and (f) represent the uncertainties in the determination of EDC peak positions. g Superconducting T_c (right axis) and superconducting gap (left axis) as a function of the energy position of the VHS in doped CsV₃Sb₅ samples (see Supplementary Figs. S12–S14). The error bars in (g) represent the uncertainties in the determination of the VHS (bottom axis), superconducting T_c (right axis), and superconducting gap (left axis).