Photoemission study of the electronic structure and charge density waves of Na2Ti2Sb2O

The electronic structure of Na 2 Ti 2 Sb 2 O single crystal is studied by photon energy and polarization dependent angle-resolved photoemission spectroscopy (ARPES). The obtained band structure and Fermi surface agree well with the band structure calculation of Na 2 Ti 2 Sb 2 O in the non-magnetic state, which indicates that there is no magnetic order in Na 2 Ti 2 Sb 2 O and the electronic correlation is weak. Polarization dependent ARPES results suggest the multi-band and multi-orbital nature of Na 2 Ti 2 Sb 2 O. Photon energy dependent ARPES results suggest that the electronic structure of Na 2 Ti 2 Sb 2 O is rather two-dimensional. Moreover, we find a density wave energy gap forms below the transition temperature and reaches 65 meV at 7 K, indicating that Na 2 Ti 2 Sb 2 O is likely a weakly correlated CDW material in the strong electron-phonon interaction regime.