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

摘要

We present results for the momentum-resolved single-particle spectralfunction of the low-dimensional system TiOCl in the insulating state, obtainedby a combination of ab initio Density Functional Theory (DFT) and VariationalCluster (VCA) calculations. This approach allows to combine a realistic bandstructure and a thorough treatment of the strong correlations. We show that itis important to include a realistic two-dimensional band structure of TiOClinto the effective strongly-correlated models in order to explain the spectralweight behavior seen in angle-resolved photoemission (ARPES) experiments. Inparticular, we observe that the effect of the interchain couplings is aconsiderable redistribution of the spectral weight around the Gamma point fromhigher to lower binding energies as compared to a purely one-dimensional modeltreatment. Hence, our results support a description of TiOCl as atwo-dimensional compound with strong anisotropy and also set a benchmark on thespectral features of correlated coupled-chain systems.