Related papers: Optical Properties and Correlation Effects in NaxC…

The electronic structure of Na$_x$CoO$_2$ revealed by recent photoemission experiments shows important deviations from band theory predictions. The six small Fermi surface pockets predicted by LDA calculations have not been observed as the…

We report systematic measurements using the ^{59}Co nuclear quadrupole resonance(NQR) technique on the cobalt oxide superconductors Na_{x}CoO_{2}\cdot 1.3H_{2}O over a wide Na content range x=0.25\sim 0.34. We find that T_c increases with…

We investigate the electronic structure of (Sr$_{1-x}$La$_x$)$_2$RhO$_4$ using a combination of the density functional and dynamical mean-field theories. Unlike the earlier local density approximation plus Hubbard $U$ (LDA+U) studies, we…

We investigate the spin state of LaCoO3 using state-of-the-art photoemission spectroscopy and ab initio band structure calculations. The GGA+U calculations provide a good description of the ground state for the experimentally estimated…

Measurements of polarization-dependent soft x-ray absorption reveal that the electronic states determining the low-energy excitations of Na$_{x}$CoO$_2$ have predominantly $a_{1g}$ symmetry with significant O $2p$ character. A large…

The electronic structure of CrO_2 is critically discussed in terms of the relation of existing experimental data and well converged LSDA and GGA calculations of the electronic structure and transport properties of this half metal magnet,…

The optical conductivity of single crystals of Na_xCoO_2 for $x$ = 0.57 is first reported between 295 and 30 K. In the far infrared, an "anomalous Drude" analysis leads to a carrier effective mass of 5 electron masses. That this high value…

The strength and effect of Coulomb correlations in the (superconducting when hydrated) x~1/3 regime of Na(x)CoO(2) have been evaluated using the correlated band theory LDA+U method. Our results, neglecting quantum fluctuations, are: (1)…

Optical properties of the isoelectronic compounds LaCoO$_3$ and HoCoO$_3$ has been experimentally and theoretically investigated. We've measured the real $\epsilon_1(\omega)$ and imaginary $\epsilon_2(\omega)$ parts of the dielectric…

We report infrared spectra of a Na$_{0.5}$CoO$_2$ single crystal which exhibits a sharp metal-insulator transition near 50 K due to the formation of charge ordering. In comparison with x=0.7 and 0.85 compounds, we found that the spectral…

The electronic band structures of the parent compound Na0.3CoO2 and the hydrated superconductor Na0.3CoO2.1.3H2O were evaluated using the local spin density approximation (LSDA). Systematic analysis on the bands near the Fermi surface (FS)…

We report the results of a comprehensive spectroscopic ellipsometry study of NaCu2O2, a compound composed of chains of edge-sharing Cu2+O4 plaquettes and planes of Cu1+ ions in a O-Cu1+-O dumbbell configuration, in the spectral range…

Two recent reports confirm that the newly synthesized Sr$_2$CoO$_4$ (formal oxidation state Co$^{4+}$) shows a high Curie temperature (~ 250 K), but they report different moments of 1.8 $\mu_B$ and 1 $\mu_B$ per Co. Using both commonly used…

We investigate the electronic states and the transport properties of the CoO2 plane in NaxCoO2 on the basis of the two-dimensional triangular lattice 11-band d-p model by using the fluctuation exchange approximation, where we consider the…

Using the merger of local density approximation and dynamical mean field theory, we show how electronic correlations increase the thermopower of Na$_{0.7}$CoO$_2$ by 200%. The newly revealed mechanism is an asymmetric shift of (quasi)…

Observed optical reflectivity in the infrared spectral region is compared with theoretical predictions in a strongly coupled electron-phonon system. Starting from a Froehlich Hamiltonian, the spectral functions and their temperature…

We report the reflectivity and the resistivity measurement of Ca_{2-x}Na_{x}CuO_{2}Cl_{2} (CNCOC), which has a single-CuO2-plane lattice with no orthorhombic distortion. The doping dependence of the in-plane optical conductivity spectra for…

CoO2 is the parent compound for the superconductor NaxCoO2\cdot1.3H2O and was widely believed to be a Mott insulator. We performed 59Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies on LixCoO2 (x = 0.35,…

Na$_x$CoO$_2$, the parent compound of the recently synthesized superconductor Na$_x$CoO$_2$:$y$H$_2$O, exhibits bulk antiferromagnetic order below $\sim20$ K for 0.75 $\leq x \leq$ 0.9. We have performed neutron scattering experiments in…

Band structure of metallic sodium cobaltate Na$_x$CoO$_2$ ($x$=0.33, 0.48, 0.61 0.72) has been investigated by local density approximation+Hubbard $U$ (LDA+$U$) method and within Gutzwiller approximation for the Co-$t_{2g}$ manifold.…