Electronic Structure Of La2CuO4 Research Articles

Temperature dependence of the electronic structure of La2CuO4 in the multielectron LDA+GTB approach

The band structure of La2CuO4 in antiferromagnetic and paramagnetic phases is calculated at finite temperatures by the multielectron LDA+GTB method. The temperature dependence of the band spectrum and the spectral weight of Hubbard fermions is caused by a change in the occupation numbers of local multielectron spin-split terms in the antiferromagnetic phase. A decrease in the magnetization of the sublattice with temperature gives rise to new bands near the bottom of the conduction band and the top of the valence band. It is shown that the band gap decreases with increasing temperature, but La2CuO4 remains an insulator in the paramagnetic phase as well. These results are consistent with measurements of the red shift of the absorption edge in La2CuO4 with increasing temperature.

Nuclear magnetic resonance chemical shifts and paramagnetic field modifications inLa2CuO4

The electronic structure of La2CuO4 has been investigated using first-principles cluster calculations and the chemical shieldings at the copper nucleus have been determined with several state-of-the-art quantum chemical methods. We have also calculated the copper shieldings for CuCl, which is often used as a reference substance for copper nuclear magnetic resonance shifts measurements, and found an appreciable paramagnetic contribution in agreement with precise measurements. The calculated chemical shift at the copper nucleus in La2CuO4 for an applied field parallel to the CuO2 planes is generally smaller than, but still in reasonable agreement with, the values derived from experiment with the assumption that the spin susceptibility vanishes at zero temperature. For the field perpendicular to the planes, the quantum chemical result is substantially smaller than the experimental data but in accord with a perturbation theoretical estimate. Inconsistencies in previous representations and interpretations of the copper magnetic shift data are pointed out and corrected.

The influence of the antiferromagnetism on the electronic structure of La2CuO4

The quasiparticle approach for electronic structure calculations considering strong electron correlations is given. The exact diagonalization of a multiband Hubbard Hamiltonian for a small cluster is combined with perturbation theory for intercluster hopping. The band structure of paramagnetic and antiferromagnetic La2CuO4 are discussed.

Electronic structure of La2CuO4 in the self-interaction-corrected density-functional formalism.

The electronic structure of tetragonal ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ is calculated in the self-interaction-corrected (SIC) local-spin-density (LSD) approximation. In contrast to LSD, the SIC-LSD approach reveals the experimentally observed antiferromagnetic and semiconducting ground state. The energy gap is 1.04 eV and of indirect charge-transfer character, and the Cu moment is 0.47${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$. The valence-band top states have about equal weight on the in-plane and out-of-plane O atoms. This region is dominated by O states not coupling to the Cu d states, but with a significant component of O states having Cu d-like symmetry.

Electronic structure of La2CuO4

The electronic band structure of La2CuO4 is performed using self-consistent linear muffin-tin orbital method. The 17 band complex is found to arise mainly from the overlap between Cu-3d and O-2p wavefunctions. The calculated density of states at the Fermi energy (N E F), the conduction band-width and the electronic specific heat coefficient are given.

The electronic structure of La 2 CuO 4 : Renormalization from density functional theory to strong coupling models

Abstract The electronic structure of La2CuO4 is analyzed in terms of the Density Functional (DFT) band picture. The DFT results are mapped onto a generalized multi-band Hubbard model and numerical values for the complete set of parameters are extracted. A variety of experimebts probing the high energy (1–10 eV) scale are well described. In a subsequent mapping process based on cluster studies, several low energy (≲ 1 eV) model Hamiltonians are tested and their parameters are evaluated. The insulating phase is quantitatively described by a Heisenberg model with excitation energies in good agreement with experiment. Spectra for added electrons or holes are well described by symmetric one-band models which could be the basis for a description of the superconducting state.

Renormalization from Density Functional Theory to Strong Coupling Models for the Electronic Structure of La2CuO4

AbstractStrong coupling models for the electronic structure of La2CuO4 are derived in two successive stages of renormalization. First, a three-band Hubbard model is derived using a constrained density functional approach. Second, exact diagonalization studies of finite clusters within the three band Hubbard model are used to select and map the low energy spectra onto effective one-band Hamiltonians. At each stage, some observables are calculated and found to be in quantitative agreement with experiment. The final results suggest the following models to be adequate descriptions of the low energy scale dynamics: (1) a spin 1/2 Heisenberg model for the insulating case with nearest neighbor J≈130 meV; (2) a "t–t'–J" model with nearly identical parameters for the electron and hole doped cases.

Accurate Tight-Binding Studies of Antiferromagnetic States in La2CuO4

AbstractAn accurate tight-binding parametrization of the electronic structure of La2CuO4 is used to investigate the effects of spin polarization of the Cu ion on the band structure and magnetic moment in the antiferromagnetic state. It is found that when an exchange splitting on the d(x2-y2) orbitals is imposed, a gap in the spectrum is obtained, whereas no gap is found if the splitting is imposed on all of the d orbitals or even on both d(x2 -y2) and d(z2) orbitals. This result suggests large anisotropy of the exchange field on the Cu ion.

Electronic structure of La-Cu and Y-Ba-Cu oxides: ground-state properties and photoemission spectra

The electronic structure of La2CuO4 and YBa2Cu3O7 has been evaluated within the local density approximation, using the LMTO-ASA method. The calculated lattice parameter for the La-based oxide is within 1% of the experimental value. Theoretical photoemission and inverse photoemission spectra (XPA and BIS) are presented. The spectra are dominated by the emission from the Cu sites and show a Cu d band strongly affected by the bonding with the O p levels.