Extended Data Fig. 3: Constant-energy map of ARPES spectra.
From: Pseudogap in a crystalline insulator doped by disordered metals
ARPES intensity maps of bulk black phosphorus whose surface is doped by Na at nd = 1.7 × 1014 cm−2 (top row) and K at nd = 1.0 × 1014 cm−2 (bottom row). Data are plotted at the constant energy marked on top of each panel as a function of kx and ky in the surface Brillouin zone of black phosphorus. Unlike the pair of C2 bands that cross EF, the C1 band shows a clear signature of a pseudogap with a magnitude of 235 meV for Na and 65 meV for K. This magnitude of the pseudogap is found to be nearly isotropic with in-plane k directions. The size of the area enclosed by the C1 contour of Na decreases towards EF, which reflects the backward-bending band dispersion.
