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Daniel Khomskii: Orbital-selective effects in transition metal compounds: 'molecules' in solids against magnetism

Wanneer:vr 19-02-2016 13:00 - 14:00


Close to Mott transition several novel states can appear. In particular, “molecular clusters” can be formed in the solid, such as dimers, trimers, etc. In my talk I will illustrate such phenomena, especially the dimer formation, on many examples: pyroxenes, La4Ru2O10, Li2RuO3, M1 and M2 phases of VO2, V and Cr hollandites. The concept of orbital-selective Peierls transitions will be proposed and justified. Such transitions can occur in case of strongly non-uniform hopping amplitudes for different orbitals and small intra-atomic Hund's rule coupling JH . For odd number of electrons per dimer, the dimer formation competes with the double exchange mechanism for ferromagnetism. I discuss some implications of these phenomena, and consider examples of realistic materials, in which orbital-selective phases seem to be realized.