First-Principles Theory of the Momentum-Dependent Local Ansatz for Correlated Electron System

The momentum-dependent local-ansatz (MLA) wavefunction describes well correlated electrons in solids in both the weak and strong interaction regimes. In order to apply the theory to the realistic system, we have extended the MLA to the first-principles version using the tight-binding LDA+U Hamiltonian. We demonstrate for the paramagnetic Fe that the first-principles MLA can describe a reasonable correlation energy gain and suppression of charge fluctuations due to electron correlations. Furthermore, we show that the MLA yields a distinct momentum dependence of the momentum distribution, and thus improves the Gutzwiller wavefunction.Comment: 8 Pages, 3 figures; to be published in Physics Procedi

Magnetic Phase Diagram and Skyrmions of the Hubbard Model on the Beta-Mn Type Lattice

Magnetic phase diagram for the Hubbard model on the Beta-Mn type lattice has been calculated as a function of the Coulomb interaction energy parameter U and the electron number per atom n by using the generalized Hartree-Fock approximation combined with the recursion method for electronic-structure calculations. The ferromagnetic state, the ferrimagnetic state, and the helimagnetic state as well as the 3Q multiple spin density waves (3QMSDW) states have been obtained on the U-n plane. Their detailed structures are examined with use of the Fourier analysis. It is shown that the calculated phase diagram and the Dzyaloshinskii-Moriya interaction elucidate the magnetic interactions for the itinerant-electron skyrmions in transition metal alloys and compounds on the Beta-Mn type lattice.Comment: 22 pages, 13 figure

Momentum-Dependent Local Ansatz Approach to the Quasiparticle States

Momentum-dependent local ansatz (MLA) wavefunction approach to correlated electrons in solids has been extended to the quasiparticle excited states on the basis of the Fermi liquid picture. The quasiparticle energy is derived from the MLA-base excited state wavefunction within the single-site approximation. The quasiparticle weight and quasiparticle energy have been calculated for the Hubbard model on the hypercubic lattice in infinite dimensions as well as the simple cubic lattice. By comparing the numerical results with the single-particle excitation spectra obtained by the Green function method, it is shown that the MLA excited wavefunctions describe well the quasiparticle states in the weak and intermediate Coulomb interaction regime in the high dimensional system.Comment: 20 pages, 8 figure