Local-Ansatz Approach with Momentum Dependent Variational Parameters to Correlated Electron Systems

Kakehashi, Y.; Shimabukuro, T.; Yasuda, Chitoshi

doi:10.1143/jpsj.77.114702

Cited by 15 publications

(19 citation statements)

References 26 publications

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“…Here H 0 is the Hartree-Fock energy and N is the number of atoms in the system. The correlation energy per atom ǫ c is obtained in the single-site approximation as follows: 14) We obtain self-consistent equations for the variational parameters λ (α)…”

Section: The Operatorsõmentioning

confidence: 99%

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First-Principles Momentum-Dependent Local Ansatz Wavefunction and Momentum Distribution Function Bands of Iron

Kakehashi

Chandra

2016

J. Phys. Soc. Jpn.

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We have developed a first-principles local ansatz wavefunction approach with momentum-dependent variational parameters on the basis of the tight-binding LDA+U Hamiltonian. The theory goes beyond the first-principles Gutzwiller approach and quantitatively describes correlated electron systems. Using the theory, we find that the momentum distribution function (MDF) bands of paramagnetic bcc Fe along highsymmetry lines show a large deviation from the Fermi-Dirac function for the d electrons with e g symmetry and yield the momentum-dependent mass enhancement factors. The calculated average mass enhancement m * /m = 1.65 is consistent with low-temperature specific heat data as well as recent angle-resolved photoemission spectroscopy (ARPES) data. The quantitative description of correlated electrons in solids has been one of the central issues in condensed matter physics. Band theory has been developed towards such a quantitative description by taking into account electron-electron interactions. Density functional theory (DFT) is the state-of-the-art theory along this line. The DFT is based on the Hohenberg-Kohn theorem 1) and the Kohn-Sham method. 2) The local density approximation (LDA) and the generalized gradient approximation (GGA) to the exchange correlation potential led to the development of the DFT as a quantitative theory.Although the DFT has been successful for the quantitative understanding of metals and band insulators, it has failed to provide a quantitative description of more correlated electron systems such as ǫ-Fe, 3) Fe pnictides, 4) cuprates, 5) as well as heavy-fermion * E-mail address: yok@sci.u-ryukyu.ac.jp, be published in J. Phys. Soc. Jpn. 85 (2016).

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Section: The Operatorsõmentioning

confidence: 99%

“…The Gutzwiller wavefunction, however, does not reduce to the second-order perturbation theory in the weakly correlated limit. 14) Thus, it does not quantitatively describe the properties in the weakly correlated regime.…”

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First-Principles Momentum-Dependent Local Ansatz Wavefunction and Momentum Distribution Function Bands of Iron

Kakehashi

Chandra

2016

J. Phys. Soc. Jpn.

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“…The behavior of these wavefunctions in the weak Coulomb interaction regime was not discussed seriously. Kakehashi et al 44 have recently pointed out that the wavefunctions mentioned above do not yield the exact results in the weak Coulomb interaction limit according to the Rayleigh-Schrödinger perturbation theory of the wavefunction. They proposed a new wavefunction called the momentum-dependent local ansatz (MLA) which is consistent with the perturbation theory.…”

Section: Momentum-dependent Local Ansatz Wavefunctionmentioning

confidence: 99%

Momentum-dependent local ansatz approach to correlated electrons

et al. 2014

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The wavefunction method provides us with a useful tool to describe electron correlations in solids at the ground state. In this paper we review the recent development of the momentum-dependent local ansatz wavefunction (MLA). It is constructed by taking into account two-particle excited states projected onto the local orbitals, and the momentum-dependent amplitudes of these states are chosen as variational parameters. The MLA describes accurately correlated electron states from the weak to the intermediate Coulomb interaction regime in infinite dimensions, and works well even in the strongly correlated region by introducing a new starting wavefunction called the hybrid (HB) wavefunction. The MLA-HB is therefore shown to overcome the limitation of the original local ansatz (LA) wavefunction as well as the Gutzwiller wavefunction. In particular, the calculated quasiparticle weight vs Coulomb interaction curve is shown to be close to that obtained by the numerical renormalization group approach. It is also shown that the MLA is applicable to the first-principles Hamiltonian.Comment: 32 pages, 7 figure

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“…Recently we proposed the momentum-dependent local ansatz (MLA) theory in order to describe the ground-state properties quantitatively. [32][33][34] The MLA improves the LA by taking into account all the two-particle excited states with momentum-dependent amplitudes. In particular the theory reduces to the Rayleigh-Schrödinger perturbation theory in the weak Coulomb interaction limit as it should be, and describes well the correlated electrons from the weak to strong Coulomb interaction regime.…”

Section: Introductionmentioning

confidence: 99%

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

Kakehashi

Chandra

2016

J. Phys. Soc. Jpn.

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The ground-state properties of iron-group transition metals from Sc to Cu have been investigated on the basis of the first-principles momentum dependent local ansatz (MLA) theory. Correlation energy gain is found to show large values for Mn and Fe: 0.090 Ry (Mn) and 0.094 Ry (Fe). The Hund-rule coupling energies are found to be 3000 K (Fe), 1400 K (Co), and 300 K (Ni). It is sugested that these values can resolve the inconsistency in magnetic energy between the density functional theory and the first-principles dynamical coherent potential approximation theory at finite temperatures. Charge fluctuations are shown to be suppressed by the intra-orbital correlations and inter-orbital charge-charge correlations, so that they show nearly constant values from V to Fe: 1.57 (V and Cr), 1.52 (Mn), and 1.44 (Fe), which are roughly twice as large as those obtained by the d band model. The amplitudes of local moments are enhanced by the intra-orbital and inter-orbital spin-spin correlations and show large values for Mn and Fe: 2.87 (Mn) and 2.58 (Fe). These values are in good agreement with the experimental values estimated from the effective Bohr magneton number and the inner core photoemission data. KEYWORDS: first-principles variational theory, momentum-dependent local ansatz, iron-group transition metals, electron correlations, correlation energy, charge fluctuations, amplitude of local moment * yok@sci.u-ryukyu.ac.jp, to be published in J. Phys. Soc. Jpn. 85 (2016).

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Local-Ansatz Approach with Momentum Dependent Variational Parameters to Correlated Electron Systems

Cited by 15 publications

References 26 publications

First-Principles Momentum-Dependent Local Ansatz Wavefunction and Momentum Distribution Function Bands of Iron

First-Principles Momentum-Dependent Local Ansatz Wavefunction and Momentum Distribution Function Bands of Iron

Momentum-dependent local ansatz approach to correlated electrons

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

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