Valence band and core-level photoemission of Au/Ge(001): Band mapping and bonding sites

We have used photoemission spectroscopy in order to investigate the electronic states and chemical bonding related to Au induced atomic chains on the Ge(001) surface. Angle-resolved photoemission reveals two types of dispersions around the Fermi level whose intensities strongly depend on the incident photon energy. Around $h\ensuremath{\nu}=100\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$, the band structure is dominated by an electronlike band of mainly one-dimensional (1D) character, which shows Tomonaga-Luttinger-like power-law behavior in the $k$-integrated spectral function. In contrast, lower photon energies reveal a metallic holelike dispersion which resembles the Ge bulk structure with its heavy-hole, light-hole, and split-off branches. The Au $4f$ core-level spectra show two doublets indicating two different Au bonding sites, whereas the Ge $3d$ core-level shows two surface components and one bulk component.