Fig. 2.

ARPES resolved electronic structure of p-SnSe. ARPES measures band dispersions along high-symmetry directions of Z–Γ–Z a, U–Y–U b, and Y–Γ–Y c, taken with 50 eV photon energy. The second derivative plots d and e, corresponding to a and b, respectively, are directly compared with the DFT calculations, in which the weight of Sn 5s and Se 4p orbitals are represented by light blue and yellow colours, respectively. A close-up of the top VBs along Γ – Z reveals pronounced differences between the theoretical band dispersion f and the ARPES measured results g, as highlighted by the X-shaped dashed lines. h A schematic plot of a pudding-mould shaped VB with corrugations, which leads to giant S due to the band geometry effect. The inset of h indicates the ARPES cut directions in the projected two-dimensional first Brillouin zone (BZ). i, j Comparison of stacked plots of constant energy contours at different E _B, which show good agreement between ARPES and DFT when E _B > 0.2 eV. Black squares represent the boundary of the first BZ