Momentum Dependent Band Renormalization and Surface Aging Effect on a Zone Center Electron Pocket in NaSn2As2 Revealed by Angle-Resolved Photoemission Spectroscopy

We report an angle-resolved photoemission spectroscopy study on NaSn2As2 in which a Sn 5p band is expected to provide interesting Fermi surface geometry with hole-like and electron-like curvatures. We observe the Sn 5p band forming a flower shaped Fermi surface with hole-like character around the zone center and electron-like character near the zone edge as expected from the band structure calculation. The bottom of the electron band along the Γ–L line is located around −0.5 eV which is shifted downwards by 0.1 eV from the calculation. However, the top of the valence band at the Γ point is around −0.5 eV which is shifted downwards by 0.3 eV from the theoretical prediction. In addition, a tiny electron pocket is observed around the Γ point just after the cleavage which disappears rapidly by surface aging without appreciable energy shift. NaSn2As2 exhibits momentum dependent renormalization of the bulk Sn 5p bands and harbors a surface sensitive electron pocket at the zone center.