Fig. 3: MZM in a topological vortex core.

a STM topography of CaKFe₄As₄ (scanning area: 70 nm × 70 nm). b Atom-resolved topography within the area of 5 × 5 nm². c STS spectra taken along the white arrow in a, at T = 0.45 K and B = 0 T. The direction of waterfall-like spectra plot is indicated by the black arrow. d Zero-bias conductance map measured at a magnetic field of 2 T in the area as shown in a. e Zero-bias conductance map (area: 20 nm × 20 nm) around a vortex core at T = 0.45 K and B = 2 T, the white arrows in a, e indicate the same position. f Intensity plot of dI/dV spectra along the white arrow across the vortex in e. g Waterfall-like dI/dV spectra plot within the yellow dashed box in f, with the black curve representing the spectrum at the vortex core center, and the black arrow indicates the direction of the plot. h Comparison of dI/dV spectra at vortex core (P1), middle (P2), edge (P3), and without magnetic field (SC gap). The “SC gap” spectrum is the lowest spectrum in c and measured at the same position of P3. All spatial positions are marked in e. i Comparison between the spatial dependence of the ZBCP peak height with a theoretical calculation of the MZM spatial profile (to exclude the influence of CBSs and background, each dI/dV spectrum is fitted by multi-Gaussian peaks to extract the height of ZBCP. An example of a fit is shown in Fig. 4).