Figure 2: Evolution of the Bi-2201 spectroscopic properties with overdoping.

The top-left panels show the E_p maps (E_p is the peak position for single-peak spectra, and half the peak-to-peak distance for two-peak spectra) for a, an overdoped sample with T_c=10 K and ΔT_c=2.5 K (OD10 K), and for b, an overdoped sample with T_c=7 K and ΔT_c=1.5 K (OD7 K). The white bars correspond to 5 nm. The distributions of E_p values presented in the histograms were normalized and compared with the histograms obtained in the least overdoped AG11 K sample (dashed lines). The top-right panels are simultaneously acquired topographies: white regions are physically higher than black ones. They show the superstructure common to all Bi-based cuprates^23,24. Especially in OD10 K, the smallest gaps (green) are preferentially located on the minima of the superstructure. A similar correlation between gap size and the superstructure has been reported in Bi-2212²⁵ and Bi-2223¹⁶. Our measurements further show that the preferred location of single-peak spectra (red-yellow) is also the minimum of the superstructure, suggesting that the local doping level itself is modulated.