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We investigate from first principles the proposed destruction of the controversial eg pockets in the Fermi surface of NaxCoO2 due to Na disorder, by calculating its k-dependent configurational averaged spectral function <A(k,w)>. To this end, a Wannier function based method is developed that treats the effects of disorder beyond the mean field. Remarkable spectral broadenings of order ~eV are found for the oxygen orbitals, possibly explaining their absence in the experiments. Contrary to the current lore, however, the eg pockets remain almost perfectly coherent. The developed method is expected to generate exciting opportunities in the study of the countless functional materials that owe their important electronic properties to disordered dopants.
We report a first-principles Wannier function study of the electronic structure of PdTe. Its electronic structure is found to be a broad three-dimensional Fermi surface with highly reduced correlations effects. In addition, the higher filling of the
The polarized Raman spectra from ab and ac surfaces of single crystal NaxCoO2 (x~0.7), parent compound of recently discovered superconductor NaxCoO2.yH2O, are reported and discussed. The crystals were hexagon platelets of typical size 3x3x0.1 mm. Thr
We study hydrogen doping effects in an iron-based superconductor LaFeAsO_(1-y) by using the first-principles calculation and explore the reason why the superconducting transition temperature is remarkably enhanced by the hydrogen doping. The present
High-temperature superconductivity occurs as copper oxides are chemically tuned to have a carrier concentration intermediate between their metallic state at high doping and their insulating state at zero doping. The underlying evolution of the electr
Performing the first-principles calculations, we investigate the anisotropy in the superconducting state of iron-based superconductors to gain an insight into their potential applications. The anisotropy ratio $gamma_lambda$ of the c-axis penetration