Using $t_{ 2g}$ Wannier-functions, a low-energy Hamiltonian is derived for orthorhombic $3d^{ 1}$ transition-metal oxides. Electronic correlations are treated with a new implementation of dynamical mean-field theory for non-cubic systems. Good agreement with photoemission data is obtained. The interplay of correlation effects and cation covalency (GdFeO$_{ 3}$-type distortions) is found to suppress orbital fluctuations in LaTiO$_{ 3},$ and even more in YTiO$_{ 3}$, and to favor the transition to the insulating state.
Categories: cond-mat.str-el