Effective one-band models for the 1D cuprate Ba_2-xSr_xCuO_3+δ

We consider a multiband Hubbard model H_m for Cu and O orbitals in Ba_2-xSr_xCuO_3+δ similar to the tree-band model for two-dimensional (2D) cuprates. The hopping parameters are obtained from maximally localized Wannier functions derived from ab initio calculations. Using the cell perturbation method, we derive both a generalized t-J model H_tJ and a one-band Hubbard model H_H to describe the low-energy physics of the system. H_tJ has the advantage of having a smaller relevant Hilbert space, facilitating numerical calculations, while additional terms should be included in H_H to accurately describe the multi-band physics of H_m. Using H_tJ and DMRG, we calculate the wave-vector resolved photoemission and discuss the relevant features in comparison with recent experiments. In agreement with previous calculations, we find that the addition of an attractive nearest-neighbor interaction of the order of the nearest-neighbor hopping shifts weight from the 3 k_F to the holon-folding branch. Kinetic effects also contribute to this process.