Mott transition and suppression of orbital fluctuations in orthorhombic 3d¹ perovskites

A many-body method which allows for a quantitative, material-specific description of the Mott transition and the orbital physics of 3d¹ perovskites is discussed. A low-energy Hamiltonian is derived for orthorhombic 3d¹ transition-metal oxides using t_2g Warnier functions. A new implementation of dynamical mean-field theory for noncubic systems is used to treat electronic correlations, and a good agreement with photoemission data is obtained. It is found that an interplay of correlation effects and cation covalency (GdFeO₃-type distortions) is responsible for the suppression of orbital fluctuations in LaTiO₃ and in YTiO ₃.