First principle cluster DMFT study of the metal insulator transition in 3d oxides

Alexander Poteryaev

Centre de Physique Theorique, Ecole Polytechnique, F-91128 Palaiseau CEDEX, France

Transition metal oxides have been studied for decades because of their unusual electronic and magnetic properties arising from narrow 3d bands and strong Coulomb correlations. The modern dynamical mean field theory is used to describe the metal insulator transition in the lighter oxides. We present an ab initio quantum theory of the metal insulator transition in Ti2O3. There is a strong competition between local Coulomb interaction and chemical bonding in a M-M pair which results in a small insulating gap of a low temperature phase. The state of the art calculations in the local density approximation (LDA) show that the bonding-antibonding splitting is not enough to open a gap and correlation effects are important. The conventional single site dynamical mean filed theory (DMFT) cannot reproduce an insulating phase for any reasonable values of the local Coulomb interaction since it leads to the reduction of the bonding-antibonding splitting. The new cluster LDA+DMFT scheme is applied to describe the many-body features of these compounds. We have investigated the metal-insulator transition in Ti2O3 and have shown that the many body effects related to the non-local Coulomb interactions are essential for a simultaneous description of the low-temperature insulating and high-temperature metallic states.