Showing papers by "Tanusri Saha-Dasgupta published in 2001"

Band-Structure Trend in Hole-Doped Cuprates and Correlation with T c max

Abstract: By calculation and analysis of the bare conduction bands in a large number of hole-doped high-temperature superconductors, we have identified the range of the intralayer hopping as the essential, material-dependent parameter. It is controlled by the energy of the axial orbital, a hybrid between $\mathrm{Cu}4s$, apical-oxygen ${2p}_{z}$, and farther orbitals. Materials with higher ${T}_{c\mathrm{max}}$ have larger hopping ranges and axial orbitals more localized in the ${\mathrm{CuO}}_{2}$ layers.

Ab initio study of disorder effects on the electronic and magnetic structure of Sr 2 FeMoO 6

Abstract: We have investigated the electronic structure of ordered and disordered Sr2FeMoO6 using ab initio bandstructure methods The effect of disorder was simulated within supercell calculations to realize several configurations with mis-site disorders It is found that such disorder effects destroy the half-metallic ferromagnetic state of the ordered compound It also leads to a substantial reduction of the magnetic moments at the Fe sites in the disordered configurations Most interestingly, it is found for the disordered configurations that the magnetic coupling within the Fe sublattice as well as that within the Mo sublattice always remain ferromagnetic, while the two sublattices couple antiferromagnetically, in close analogy to the magnetic structure of the ordered compound, but,in contrast to recent suggestions

Modeling the Electronic Behavior of γ-LiV 2 O 5 : A Microscopic Study

Abstract: We determine the electronic structure of the one-dimensional spin- $\frac{1}{2}$ Heisenberg compound $\ensuremath{\gamma}\ensuremath{-}{\mathrm{LiV}}_{2}{\mathrm{O}}_{5}$, which has two inequivalent vanadium ions, V(1) and V(2), via density-functional calculations. We find a relative V(1)-V(2) charge ordering of roughly 70:30. We discuss the influence of the charge ordering on the electronic structure and the magnetic behavior. We give estimates of the basic hopping matrix elements and compare with the most studied ${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{NaV}}_{2}{\mathrm{O}}_{5}$.

Electronic structure of and covalency driven metal-insulator transition in BaCo 1−x Ni x S 2

Abstract: We investigate the evolution of the electronic structure across the metal-to-insulator transition in the isostructural series, BaCo 1−x Ni x S 2 , using electron spectroscopic studies. Our experimental results show a progressive depletion of the spectral intensity at and near the Fermi level across the series, with decreasing x. Analysis of the core-level and valence-band photoemission spectra in conjunction with detailed many-body calculations show that the ground state of the system is highly covalent. We estimate the electronic structure parameters of the system and deduce that the hopping interaction strength t pd decreases in the solid solution with a decrease of the Ni content, while U dd and Δ do not change appreciably. Thus, the metal-to-insulator transition in this system is found to be driven primarily by covalency effects, though the static disorder in the system is expected to play an important role in determining the details of physical properties.