Figure 1: Crystal structure and electronic structure of monolayer PtSe2.

(a) Crystal structure of monolayer PtSe2 (top: unit cell, bottom: top view). (b) Band dispersions along the K-Γ-M-K direction from first-principles calculations. The colour and line width distinguish the contribution from Pt and Se (Red for Se and green for Pt). (c) Low-energy electron diffraction (LEED) pattern of as-grown monolayer PtSe2 on Pt(111). The peaks from PtSe2 are pointed by blue arrows. Additional diffraction spots rotated from the PtSe2 spots are much weaker and at different azimuthal angles and the measured band dispersions in h do not show contributions from them, which are expected at different azimuthal angles. (d) ARPES data measured along M-Γ-M direction. (e) ARPES data measured along the K-Γ-K direction. (f) Energy distribution curves (EDCs) for data shown in d for momentum range between the arrows. (g) The EDC at Γ point, from which we can resolve the four bands. (h) Constant energy maps at selected energies. The contours of the top four bands at positive kx are highlighted by coloured lines.