Figure 1: Electronic structure of the as-prepared double-layer FeSe/SrTiO ₃ film.

The data were taken on double-layer FeSe/SrTiO₃ film after the sample was annealed at 190 °C in vacuum for 1 h to remove the amorphous Se-capping layer. This sample contains the pure N phase. (a) Band structure along the cut 1 crossing the Γ point. Its corresponding second derivative image with respect to energy is shown in b. A hole-like band is observed labelled as N1. (c) Band structure for the cut 2 crossing the M2 point and its corresponding second derivative image is shown in d. (e) Band structure along the cut 3 crossing the M3 point with its corresponding second derivative image is shown in f. A hole-like band labelled as N2 is marked in f. It is strong on the left side, but weak on the right side possibly due to the photoemission matrix element effect. Another hole-like band N3 is also observed. (g–i) Photoemission spectra (energy distribution curves, EDCs) for the cut 1, cut 2 and cut 3, respectively. The EDCs at high symmetry points are marked in red, and the EDCs near the top of the N2 band are marked in blue. (j) Fermi surface of the as-prepared double-layer FeSe/SrTiO₃ film obtained by integrating the spectral weight near a small energy window (−0.03 eV,−0.01 eV) near the Fermi level. The three momentum cuts (cut 1, cut 2 and cut 3) are marked in the figure. For convenience, the four Brillouin zone corners are labelled as M1, M2, M3 and M4.