Generic phase diagram of "electron-doped" T' cuprates

We investigated the generic phase diagram of the electron doped superconductor, Nd2-xCexCuO4, using films prepared by metal organic decomposition. After careful oxygen reduction treatment to remove interstitial Oap atoms, we found that the Tc increases monotonically from 24 K to 29 K with decreasing x from 0.15 to 0.00, demonstrating a quite different phase diagram from the previous bulk one. The implication of our results is discussed on the basis of tremendous influence of Oap "impurities" on superconductivity and also magnetism in T' cuprates. Then we conclude that our result represents the generic phase diagram for oxygen-stoichiometric Nd2-xCexCuO4.Comment: 12 pages, 4 figures; International Symposium on Superconductivity (ISS) 200

Long-range interactions in the effective low energy Hamiltonian of Sr2IrO4: a core level resonant inelastic x-ray scattering study

We have investigated the electronic structure of Sr2IrO4 using core level resonant inelastic x-ray scattering. The experimental spectra can be well reproduced using ab initio density functional theory based multiplet ligand field theory calculations, thereby validating these calculations. We found that the low-energy, effective Ir t2g orbitals are practically degenerate in energy. We uncovered that covalency in Sr2IrO4, and generally in iridates, is very large with substantial oxygen ligand hole character in the Ir t2g Wannier orbitals. This has far reaching consequences, as not only the onsite crystal-field energies are determined by the long range crystal-structure, but, more significantly, magnetic exchange interactions will have long range distance dependent anisotropies in the spin direction. These findings set constraints and show pathways for the design of d^5 materials that can host compass-like magnetic interactions