Fig. 4: Distinct superconducting state in CsV_2.6Ta_0.4Sb₅.

a Schematic of the Fermi surface of CsV_2.6Ta_0.4Sb₅. The gapless (gapped) momentum regions are shown in red (blue). Symmetrized EDCs at selected momentum points (marked by i, ii, and iii) are presented. The overlaid curves represent the fitting results by the Norman function. The orange arrow indicates the scattering wavevector Q_p connecting the circular Fermi pocket around Γ. b Schematic of the band structure along the K-M direction and the electron density of states associated with the VHS. c, d Same as (a), (b), but for the pristine CsV₃Sb₅. e, f Spatially averaged dI/dV spectrum of CsV_2.6Ta_0.4Sb₅ (e) and CsV₃Sb₅ (f) measured at 0.4 K. g Waterfall-like plot of the dI/dV spectra, showing a uniform superconducting gap along a line-cut on CsV_2.6Ta_0.4Sb₅. h Simulated QPI pattern calculated by the autocorrelation of the approximate schematic of the Fermi surface. i–l Six-fold symmetrized Fourier transform of dI/dV maps measured on the Sb surface of CsV_2.6Ta_0.4Sb₅ at 0.4 K, with an energy of −0.9 meV, −0.7 meV, −0.5 meV, and 0 meV, respectively. m dI/dV spectra measured at 0 Tesla (T) and 1 T. n Δg plotted as a function of energy. o Same as (n), but measured with a magnetic field of 1 T. p, q Same as (k), (l), but measured with a magnetic field of 1 T. The unsymmetrized raw data of the Fourier transform of dI/dV maps and STM setup conditions are shown in Supplementary Fig. S16.