Momentum-resolved single-particle spectral function for TiOCl from a combination of density functional and variational cluster calculations

We present results for the momentum-resolved single-particle spectral function of the low-dimensional system TiOCl in the insulating state, obtained by a combination of ab initio density functional theory and variational cluster approach calculations. This approach allows to combine a realistic band structure and a thorough treatment of the strong correlations. We show that it is important to include a realistic two-dimensional band structure of TiOCl into the effective strongly correlated models in order to explain the spectral-weight behavior seen in angle-resolved photoemission spectroscopy experiments. In particular, we observe that the effect of the interchain couplings is a considerable redistribution of the spectral weight around the Γ point from higher to lower binding energies as compared to a purely one-dimensional model treatment. Hence, our results support a description of TiOCl as a two-dimensional compound with strong anisotropy and also set a benchmark on the spectral features of correlated coupled-chain systems.