Photoemission and Hartree-Fock study of some layered t2g-electron systems

Takashi Mizokawa

Department of Complexity Science and Engineering, University of Tokyo, 5-1-5 Kashiwanoha, 277-8561 Kashiwa, Japan

By using photoemission spectroscopy and model Hartree-Fock calculation, we have studied the electronic structures of two-dimensional t2g systems: the layered Co oxides with Co-O triangular lattice and the layered perovskite Ca2-xSrxRuO4. The valence band photoemission data of hole doped Co-O triangular lattice compounds show that the t2g bands near the Fermi level are strongly renormalized by the electron-electron and electron-lattice interactions. The model Hartree-Fock calculation for the Co-O triangular lattice indicates that some spin and charge orderings are favored for hole concentration of 1/3 and 2/3. On the other hand, the photoemission data of Ca2-xSrxRuO4 show that the t2g bands are moderately renormalized in the metallic phase. Among the three t2g bands, the gamma (xy) band is substantially broadened in the Ca rich region. The model Hartree-Fock calculation is employed to explain the evolution of the Fermi surface and the resultant orbital change as a function of Ca doping.