First-Principles Theory of Momentum Dependent Local Ansatz Approach to Correlated Electron System

Abstract

We have extended the momentum-dependent local-ansatz (MLA) wavefunction method to the first-principles version using the tight-binding LDA+U Hamiltonian for the description of correlated electrons in the real system. The MLA reduces to the Rayleigh-Schrödinger perturbation theory in the weak correlation limit, and describes quantitatively the ground state and related low-energy excitations in solids. The theory has been applied to the paramagnetic Fe. The role of electron correlations on the energy, charge fluctuations, amplitude of local moment, momentum distribution functions, as well as the mass enhancement factor in Fe has been examined as a function of Coulomb interaction strength. It is shown that the inter-orbital charge-charge correlations between d electrons make a significant contribution to the correlation energy and charge fluctuations, while the intra-orbital and inter-orbital spin-spin correlations make a dominant contribution to the amplitude of local moment and the mass enhancement in Fe. Calculated partial mass enhancements are found to be 1.01, 1.01, and 3.33 for s, p, and d electrons, respectively. The averaged mass enhancement 1.65 is shown to be consistent with the experimental data as well as the recent results of theoretical calculations.

First-Principles Momentum Dependent Local Ansatz Approach to the Momentum Distribution Function in Iron-Group Transition Metals

“…ατ LL ′ are spin independent (, i.e.,λ ατ LL ′ ), and the self-consistent equations are expressed as follows. 31)…”

“…τ LL ′ are expressed by the Laplace transforms of the Hartree-Fock local densities of states. 31) It should be noted thatQ LL ′ , P LL ′ , and K (13). The Fermi level ǫ F is determined by the conduction electron number per atom n e , which is expressed as…”

“…Quit recently, we extended the MLA to the first-principles version combining the theory with the first-principles tight-binding LDA+U Hamiltonian. 30,31) On the basis of the first principles MLA, we calculated the correlation energy, charge fluctuations, amplitude of local moment, and the momentum distribution function for paramagnetic iron, and clarified the ground-state property. 31) Subsequently, we investigated the correlation energy, charge 2/35 fluctuations, and the amplitude of local moment of the iron-group transition metals in the paramagnetic state using the same theory, and clarified the correlation effects on these quantities.…”

“…30,31) On the basis of the first principles MLA, we calculated the correlation energy, charge fluctuations, amplitude of local moment, and the momentum distribution function for paramagnetic iron, and clarified the ground-state property. 31) Subsequently, we investigated the correlation energy, charge 2/35 fluctuations, and the amplitude of local moment of the iron-group transition metals in the paramagnetic state using the same theory, and clarified the correlation effects on these quantities. 32) In this paper, we investigate the momentum distribution functions (MDF) and mass enhancement factors (MEF) of the iron-group transition metals from Sc to Cu on the basis of the first-principles MLA in order to understand their systematic change over the 3d series.…”

First-Principles Momentum Dependent Local Ansatz Approach to the Ground-State Properties of Iron-Group Transition Metals

“…τ LL ′ are expressed by means of the Laplace transforms of the Hartree-Fock local densities of states. 35 It should be noted thatQ LL ′ , P LL ′ , and K…”