Fermi-liquid-type spectral function and angle resolved photoelectron spectra of the $Ti-3d_{z^2}$-band of $TiTe_2$

Angle and temperature dependent photoelectron spectra with high energy and momentum resolution (ΔE = 300meV, Δθ< ±0.5°) were taken near the Fermi energy (Eb < 1eV) of the quasi-two-dimensional, metallic layer compound TiTe2 along the direction ΓM. The aim was to test the range of the validity of the Fermi liquid model using a Taylor expansion for the self-energy used by Claessen et al. [1] for a system whose low energy properties are those of a normal metal. Single crystalline samples have been prepared by vapor growth technique using different amounts of Te in order to influence the intercalation of surplus Ti. We found a dependence of the dispersion of the Ti-3dz2-derived band on the stoichiometry of the samples. For an exact line shape analysis the spectra were fitted by a least-squares-method to a Fermi-liquid-type spectral function taking into account the crucial effects due to the apparatus, as there are the energy resolution and finite angle resolution which leads to a limited integration in k-space. In the region where the Ti-3dz2-derived band crosses the Fermi level we found excellent agreement between the experimental line shape and the Fermi liquid model. On the other hand there are distinct deviations between the theoretical and the experimental line shape at the Brillouin zone boundary even for a self-energy proposed by Matho [2] without Taylor expansion