Combining density-functional and dynamical-mean-field theory for La1-xSrxTiO3

The dynamical-mean-held theory combined with the noncrossing approximation is used to set up a scheme to study the electronic structure of strongly co rrelated electron systems. The noninteracting band structure is obtained fr om a density-functional calculation within the local-density approximation. With this method the doped Mott insulator La1-xSxTi O-3 is studied. Starti ng from first-principle calculations for a cubic and an orthorhombic system we determine the one-particle spectrum. Both one-particle spectra show a l ower Hubbard band (seen as d(1)-->d(0) transitions in photoemission experim ents) and a quasiparticle resonance near the Fermi energy and the upper Hub bard band (d(1)-->d(2) transitions in an inverse photoemission experiment). The upper Hubbard band develops a multipeak structure, a consequence of th e consideration of all local two-particle correlations, which leads to the full multiplet structure in the atomic limit. The calculation for the ortho rhombic system shows qualitative good agreement when compared with experime ntal photoemission spectra.