Electronic Structure of Strongly Correlated Systems Emerging from Combining Path-Integral Renormalization Group with the Density-Functional Approach

Imai, Yoshiki; Solovyev, I. V.; Imada, Masatoshi

doi:10.1103/physrevlett.95.176405

Cited by 73 publications

(114 citation statements)

References 31 publications

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“…34. Thus, we believe that it poses a severe test for the proposed method, and the obtained results should clearly demonstrate that our general strategy, which can be expressed by the formula first-principles electronic structure calculations → construction of the model Hamiltonian → solution of the model Hamiltonian, 5,34 is indeed very promising. For example, at the HF level, using relatively simple model Hamiltonian, which is limited exclusively by the t 2g bands, we will be able to reproduce the main results of all-electron calculations.…”

Section: Introductionmentioning

confidence: 86%

“…The magnitude of the correlations energy depends on the magnetic state and is expected to be larger in the case of the AFM spin alignment, where the net magnetization is zero and the choice of the many-electron wave function in the form of a single Slater determinant is always an approximation. 5 On the other hand, the saturated ferromagnetic state can be described relatively well by a single Slater determinant. All these trends are clearly seen in the total energy calculations, which take into account the correlation effect in the second order of perturbation theory (Table III).…”

Section: Low-temperature Orthorhombic Phase (T < 77 K)mentioning

confidence: 99%

“…In such a situation, it is perhaps more practical to derive an approximate ground state from the diagonalization of a many-electron Hamiltonian matrix constructed in the basis of some limited number of specially selected Slater determinants, as it is done for example in the path-integral renormalization group method. 5,60 Thus, one of the challenging problems in the theory of distorted perovskite oxides remains to be the explanation of the G-type AFM ground state in LaTiO 3 . Definitely, we need a more rigorous theory for the correlation effects.…”

Section: Latio3mentioning

confidence: 99%

“…These electrons are subjected to the strong intraatomic Coulomb repulsion, which is not properly treated by LDA and requires some considerable improvement of this approximation, which currently processes in the direction of merging LDA with various model approaches for the strongly-correlated systems. 2,3,4,5 Nevertheless, LDA continues play an important role for these systems as it naturally incorporates into the model analysis the effects of the lattice distortion, and does it formally without any adjustable parameters. Although the origin of the lattice distortion in the t 2g perovskite oxides is not fully understood, is is definitely strong and exhibits an appreciable material-dependence, which can be seen even visually in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Lattice distortion and magnetism of3d−t2gperovskite oxides

Solovyev

2006

Phys. Rev. B

150

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Several puzzling aspects of interplay of the experimental lattice distortion and the the magnetic properties of four narrow t2g-band perovskite oxides (YTiO3, LaTiO3, YVO3, and LaVO3) are clarified using results of first-principles electronic structure calculations. First, we derive parameters of the effective Hubbard-type Hamiltonian for the isolated t2g bands using newly developed downfolding method for the kinetic-energy part and a hybrid approach, based on the combination of the random-phase approximation and the constraint local-density approximation, for the screened Coulomb interaction part. Apart form the above-mentioned approximation, the procedure of constructing the model Hamiltonian is totally parameter-free. The results are discussed in terms of the Wannier functions localized around transition-metal sites. The obtained Hamiltonian was solved using a number of techniques, including the mean-field Hartree-Fock (HF) approximation, the second-order perturbation theory for the correlation energy, and a variational superexchange theory, which takes into account the multiplet structure of the atomic states. We argue that the crystal distortion has a profound effect not only on the values of the crystal-field (CF) splitting, but also on the behavior of transfer integrals and even the screened Coulomb interactions. Even though the CF splitting is not particularly large to quench the orbital degrees of freedom, the crystal distortion imposes a severe constraint on the form of the possible orbital states, which favor the formation of the experimentally observed magnetic structures in YTiO3, YVO3, and LaVO3 even at the level of mean-field HF approximation. It is remarkable that for all three compounds, the main results of all-electron calculations can be successfully reproduced in our minimal model derived for the isolated t2g bands. We confirm that such an agreement is only possible when the nonsphericity of the Madelung potential is explicitly included into the model. Beyond the HF approximation, the correlations effects systematically improve the agreement with the experimental data. Using the same type of approximations we could not reproduce the correct magnetic ground state of LaTiO3. However, we expect that the situation may change by systematically improving the level of approximations for dealing with the correlation effects.

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Section: Introductionmentioning

confidence: 86%

Section: Low-temperature Orthorhombic Phase (T < 77 K)mentioning

confidence: 99%

Section: Latio3mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lattice distortion and magnetism of3d−t2gperovskite oxides

Solovyev

2006

Phys. Rev. B

150

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“…8,9 While the system could not be driven toward superconductivity, it turned out to be a model system for studying the interplay of orbital-lattice, spin-orbital, and superexchange interactions. [10][11][12][13] In tetragonal Sr 2 VO 4 with space group I 4 /mmm, 14,15 the octahedrally coordinated V 4+ ions occupy a square lattice in the ab plane (see Fig. 1).…”

mentioning

confidence: 99%

Alternating spin-orbital order in tetragonal Sr2VO4

et al. 2011

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Considering spin-orbit coupling, the tetragonal crystal field, and all relevant superexchange processes including quantum interference, we derive expressions for the energy levels of the vanadium ions in tetragonal Sr 2 VO 4 . The used parameters of the model Hamiltonian allow us to describe well the excitation spectra observed in neutron scattering and optical experiments at low temperatures. The free energy exhibits a minimum which corresponds to a novel alternating spin-orbital order with strong thermal fluctuation of the orbital mixing parameter. In many transition-metal compounds the orbital degrees of freedom play a decisive role in determining the groundstate properties of materials such as manganites, titanates, or vanadates. 1 When contributions of the orbital moment and spin-orbit coupling are not negligible, a separation between spin and orbital degrees of freedom is not adequate anymore and the system is better described by an effective total angular momentum. 2,3 If spin-orbit coupling competes with electron-phonon or exchange interactions even strong fluctuation regimes can arise. [4][5][6] The system investigated here is the layered insulator Sr 2 VO 4 with tetragonal symmetry, which early on has come into focus as an isostructural d 1 analog of La 2 CuO 4 . 7 Consequently, it was suggested that Sr 2 VO 4 could become superconducting upon applying chemical pressure by doping or external pressure. 8,9 While the system could not be driven toward superconductivity, it turned out to be a model system for studying the interplay of orbital-lattice, spin-orbital, and superexchange interactions. [10][11][12][13] In tetragonal Sr 2 VO 4 with space group I 4 /mmm, 14,15 the octahedrally coordinated V 4+ ions occupy a square lattice in the ab plane (see Fig. 1). The magnetic ground state has been claimed to be antiferromagnetic with transition temperatures in the range 10-100 K determined from susceptibility measurements, but long-range order has remained evasive on the basis of neutron-diffraction studies. 14,16,17 Recent studies have established the occurrence of a magnetostructural phase transition extending over a temperature range from 94 K to 122 K. Both the high-temperature and the low-temperature structure are tetragonal and reportedly coexist within this range. 11 Specific heat data have revealed two distinct broad maxima occurring at 98 K and 127 K mirroring the borders of the two-phase regime. 18,19 The disappearance of the high-temperature phase is accompanied by a significant drop in the susceptibility at about 100 K, which has been attributed to the onset of long-range antiferromagnetic (AFM) and orbital order. 11 Theoretically, the ground state of Sr 2 VO 4 has been interpreted in terms of stripelike orbital and collinear AFM spin order 10 or an ordering of magnetic octupoles. 12 Inelastic neutron scattering has revealed two excitations at about 120 meV, which have been assigned to the highest lying doublet of the V 4+ t 2g levels. 13 Recent optical experiments have reported excitations at 31 ...

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Charge Dynamics in Layered Nickelates with Charge-Ordering Instability

Uchida

2013

Springer Theses

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Electronic Structure of Strongly Correlated Systems Emerging from Combining Path-Integral Renormalization Group with the Density-Functional Approach

Cited by 73 publications

References 31 publications

Lattice distortion and magnetism of3d−t2gperovskite oxides

Lattice distortion and magnetism of3d−t2gperovskite oxides

Alternating spin-orbital order in tetragonal Sr2VO4

Charge Dynamics in Layered Nickelates with Charge-Ordering Instability

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