Fig. 2

QPI patterns and the FFT images at different bias energies. a–d Series of FFT images transformed from the measured dI/dV maps, with the bias voltages of +100, +40, −40, and −80 mV respectively. The length of the scale bar is 0.5 Å⁻¹. The dI/dV maps are measured on the same region as shown in Fig. 1e, f. The colored ovals represent the scattering q vectors as indicated in e. All the FFT images are symmetrized and drift-corrected. e Schematic band structure along the Y–Γ–Y direction. The intra- and inter-band scatterings are marked by the red arrows. The q₁ represents the intra-band scattering of the conduction band, which forms the pink ovals (a–d). The q₂ represents the inter-band scattering between the two conduction bands, which forms the green ovals in a–d. The q₃ represents the inter-band scattering between the valence band and conduction band, which forms the orange oval in c and d. The q₄ represents the intra-band scattering of the valence band, which forms the red oval in d. f E-q dispersion along the Y–Γ–Y direction. In the region labeled by 2D-FFT, from −80 to +100 mV, the dispersion is extracted from the line-cut profiles in the 2D-FFT images in the Supplementary Figure 5. The position of the line-cut is marked by the black line in a. In the regions labeled by 1D-FFT, from −200 to −80 mV and from +100 to +200 mV, the dispersion is extracted from the 1D-FFT of the dI/dV spectroscopic map taken along the y axis (See Supplementary Figure 6). The black lines schematically illustrate the band dispersion of q₂, q₃, and q₄