Electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Ca</mml:mi><mml:msub><mml:mi mathvariant="normal">Cu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>: Spin ladder versus one-dimensional spin chain

Bordas, Esther; Graaf, Coen de; Caballol, Rosa; Calzado, Carmen J.

doi:10.1103/physrevb.71.045108

Cited by 31 publications

(27 citation statements)

References 49 publications

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“…This approach is reasonable since t ab is only moderatly dependent on the electronic correlation as it has been shown in the past for several authors in quite different systems. 33 …”

Section: ͑4͒mentioning

confidence: 97%

“…This procedure makes use of the effective Hamiltonian theory, and it has been previously used in the study of magnetic systems, as well as the evaluation of hopping integrals in mixed-valence systems. [29][30][31][32][33][34][35][36][37][38][39][40][41] A detailed description of the method can be found in Ref. 41, and a summary enlightening the most striking points will be provided here.…”

Section: ͑4͒mentioning

confidence: 99%

“…This strategy has been extensively used in the recent past, especially in the evaluation of magnetic coupling constants as well as the determination of hopping integrals in numerous systems. [29][30][31][32][33][34][35][36][37][38][39][40][41]46,48,49,61,62 The whole procedure can be summarized as follows. ͑1͒ A fragment of the bulk structure of TiO 2 has been chosen, containing two neighbor Ti centers, and the ten oxygen atoms around them, as shown in Fig.…”

Section: Approximation To the Exact N-electron Wave Functionsmentioning

confidence: 99%

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Effect of on-site Coulomb repulsion termUon the band-gap states of the reduced rutile (110)TiO2surface

2008

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We present a study concerning the effect of the on site d-d Coulomb interaction energy U on the band-gap states of nonstoichiometric rutile ͑110͒ TiO 2 surface. As well known, the excess electrons resulting from the formation of oxygen vacancies localize on the Ti 3d orbitals forming band-gap states. Local density approximation ͑LDA͒ does not give a correct description of these band-gap states, either with or without gradient corrections. The failure of LDA is often attributed to an inadequate treatment of electron correlation in systems with localized orbitals and is commonly corrected with an empirical local Coulomb repulsion term, i.e., the LDA+ U method. This study provides a completely general strategy to estimate the U value in this kind of systems, illustrated here for reduced ͑110͒ TiO 2 surface, well characterized from experiments. From ab initio embedded cluster configuration interaction calculations, combined with the effective Hamiltonian theory, a value of U of 5.5± 0.5 eV is obtained, in good agreement with those reported for this system from x-ray photoemission spectroscopy experiments ͑U = 4.5± 0.5 eV͒. It is observed that when the ab initio estimate of U is injected into the periodic LDA+ U calculations, a correct description of the gap states is obtained from the periodic LDA+ U calculations. Additionally, the results indicate that the position of these states on the band gap strongly depends on the level at which lattice relaxation is taken into account, with significant differences between the density of states curves at the LDA+ U level obtained using the optimal generalized gradient approximation or LDA+ U geometries. These results suggest that this combined strategy could be a useful tool for those systems where electron correlation plays a key role, and no experimental data are available for the on-site Coulomb repulsion.

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“…This approach is reasonable since t ab is only moderatly dependent on the electronic correlation as it has been shown in the past for several authors in quite different systems. 33 …”

Section: ͑4͒mentioning

confidence: 97%

Section: ͑4͒mentioning

confidence: 99%

Section: Approximation To the Exact N-electron Wave Functionsmentioning

confidence: 99%

See 1 more Smart Citation

Effect of on-site Coulomb repulsion termUon the band-gap states of the reduced rutile (110)TiO2surface

2008

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“…It is known, 7,43,44 however, that DDCI/IDDCI brings rather small corrections to the CASCI/CASSCF estimates for the nearest-neighbor hoppings on two-plaquette clusters in various cuprates, not larger than 15%. 43,44 This suggests that dynamical electron correlation is not essential in determining the magnitude of the hopping integrals, as already pointed out in Refs. 43 and 44, for example.…”

Section: Renormalization Of the Hopping Integrals By Spin Interamentioning

confidence: 99%

Renormalization of quasiparticle hopping integrals by spin interactions in layered copper oxides

2007

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Holes doped within the square CuO 2 network specific to the cuprate superconducting materials have oxygen 2p character. We investigate the basic properties of such oxygen holes by wave-function-based quantum chemical calculations on large embedded clusters. We find that a 2p hole induces ferromagnetic correlations among the nearest-neighbor Cu 3d spins. When moving through the antiferromagnetic background, the hole must bring along this spin-polarization cloud at nearby Cu sites, which gives rise to a substantial reduction of the effective hopping parameters. Such interactions can explain the relatively low values inferred for the effective hoppings by fitting the angle-resolved photoemission data. The effect of the background antiferromagnetic couplings of renormalizing the effective nearest-neighbor hopping is also confirmed by densitymatrix renormalization-group model-Hamiltonian calculations for chains and ladders of CuO 4 plaquettes.

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“…In fact, such interactions are expected to be crucial for explaining unusual magnetic behavior in 3 He absorbed on graphite 4,5 , Wigner crystals 6 and some Mott insulators on triangular lattices. 7 The relevance of the four-spin cyclic exchange has also been reported [8][9][10][11][12][13][14][15][16][17] A second motivation to investigate multiple-spin exchange interactions stems from the exotic physics that emerges from their competition with the Heisenberg spin exchange. For instance, certain sorts of spin nematic phases are known to be stabilized in some two-dimensional Heisenberg magnets with ring-exchange interaction.…”

Section: Introductionmentioning

confidence: 98%

Semiclassical approach to competing orders in a two-leg spin ladder with ring exchange

2012

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We investigate the competition between different orders in the two-leg spin ladder with a ring-exchange interaction by means of a bosonic approach. The latter is defined in terms of spin-1 hardcore bosons which treat the Néel and vector chirality order parameters on an equal footing. A semiclassical approach of the resulting model describes the phases of the two-leg spin ladder with a ring-exchange. In particular, we derive the lowenergy effective actions which govern the physical properties of the rung-singlet and dominant vector chirality phases. As a by-product of our approach, we reveal the mutual induction phenomenon between spin and chirality with, for instance, the emergence of a vector-chirality phase from the application of a magnetic field in bilayer systems coupled by four-spin exchange interactions.

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Electronic structure ofCaCu2O3: Spin ladder versus one-dimensional spin chain

Cited by 31 publications

References 49 publications

Effect of on-site Coulomb repulsion termUon the band-gap states of the reduced rutile (110)TiO2surface

Effect of on-site Coulomb repulsion termUon the band-gap states of the reduced rutile (110)TiO2surface

Renormalization of quasiparticle hopping integrals by spin interactions in layered copper oxides

Semiclassical approach to competing orders in a two-leg spin ladder with ring exchange

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