Electron band structure of a rare-earth metal: Tb(0001)

The electron band structure of Tb metal has been determined at room temperature by means of angle-resolved photoemission experiments on Tb(0001). For the first time in any rare-earth metal, the full dispersed 6s-5${\mathit{d}}_{3\mathit{z}}^2$-1-type ${\mathrm{\Delta }}_1$ band has been experimentally mapped along the ΓΔA line. The two critical points of the ${\mathrm{\Delta }}_1$ band have been determined at ${\mathrm{\Gamma }}_1^{+}$=-6.9 eV and ${\mathrm{\Gamma }}_4^{\mathrm{-}}$=-3.6 eV. Dispersion and width of the initial ${\mathrm{\Delta }}_1$ band are in good agreement with relativistic linear muffin-tin orbitals calculations, but the absolute energy position deviates by -1.5 eV from theory. [${\mathrm{\Gamma }}_1^{+}$(calc)=-5.3 eV and ${\mathrm{\Gamma }}_4^{\mathrm{-}}$(calc)=-2.3 eV.] The initial ${\mathrm{\Delta }}_1$ band lies well below the Fermi level, also in agreement with theory, and the experimental value of the 4f binding energy is about -2.6 eV.