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As, Moskvin; Málek, Jiřı́; Knupfer, M.; Neudert, R.; Fink, J.; Hayn, R.; Sl, Drechsler; Motoyama, N.; Eisaki, H.; Uchida, S.

doi:10.1103/physrevlett.91.037001

Cited by 47 publications

(46 citation statements)

References 23 publications

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“…On the other hand, for E parallel to the chain direction, both types of excitons (one-and two-center's) can be observed. Indeed, the polarization-dependent angleresolved EELS study of the 1D cuprate Sr 2 CuO 3 with the corner-shared CuO 4 plaquettes has provided a unique opportunity to separate both the one-and two-center CT excitons and reveal the two-peak nature of the CT gap with the presence of nearly degenerate two types of excitations 23 . In other words, similar to RMnO 3 , insulating cuprates appear to be neither Mott-Hubbard, nor CT insulators, thus falling into intermediate region in which there are strong fluctuations between one-and two-center CT excitons.…”

Section: Ellipsometric Study Of Optical Response Of Rmno3mentioning

confidence: 99%

“…In the former the gap is formed by the transition between the lower and upper Hubbard bands (U < ∆), while in the latter it is formed by the CT transitions between upper filled ligand and upper Hubbard bands (U > ∆). Actually in both cases we deal with CT transitions, however, in terms of a classification introduced by A. Moskvin et al 22,23 these correspond to two-center (d 1 -d 2 -) and one-center (pd-) CT excitons, respectively. Usually one considers that the gap is of CT p-d type (U > ∆) for heavier transition metals (Cu, Ni, ...), while it is of d-d type (U < ∆) for the light transition metals (Ti, V, ...).…”

Section: E Some Features Of Ct Transitions In Strongly Coupled Cornementioning

confidence: 99%

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Interplay ofp−dandd−dcharge transfer transitions in rare-earth perovskite manganites

Moskvin¹,

Махнев

Nomerovannaya

et al. 2010

Phys. Rev. B

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We have performed both theoretical and experimental study of optical response of parent perovskite manganites RMnO3 with a main goal to elucidate nature of clearly visible optical features. Starting with a simple cluster model approach we addressed the both one-center (p-d ) and two-center (d-d ) charge transfer (CT) transitions, their polarization properties, the role played by structural parameters, orbital mixing, and spin degree of freedom. Optical complex dielectric function of single crystalline samples of RMnO3 (R=La, Pr, Nd, Sm, Eu) was measured by ellipsometric technique at room temperature in the spectral range from 1.0 to 5.0 eV for two light polarizations: E c and E ⊥ c. The comparative analysis of the spectral behavior of ε1 and ε2 is believed to provide a more reliable assignment of spectral features. We have found an overall agreement between experimental spectra and theoretical predictions based on the theory of one-center p-d CT transitions and intersite d-d CT transitions. Our experimental data and theoretical analysis evidence a dual nature of the dielectric gap in nominally stoichiometric matrix of perovskite manganites RMnO3, it is formed by a superposition of forbidden or weak dipole allowed p-d CT transitions and inter-site d-d CT transitions. In fact, the parent perovskite manganites RMnO3 should rather be sorted neither into the CT insulator nor the Mott-Hubbard insulator in the Zaanen, Sawatzky, Allen scheme.

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Section: Ellipsometric Study Of Optical Response Of Rmno3mentioning

confidence: 99%

Section: E Some Features Of Ct Transitions In Strongly Coupled Cornementioning

confidence: 99%

Interplay ofp−dandd−dcharge transfer transitions in rare-earth perovskite manganites

Moskvin¹,

Махнев

Nomerovannaya

et al. 2010

Phys. Rev. B

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“…2. 10,12 Note that the peak C ′ was observed only with q ∼ 0. Although the peak at 5.2 eV is missing in our measurement, the previously reported σ(ω) by Imada et al also show a small peak there.…”

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confidence: 99%

“…S. Moskvin et al investigated the electronic structure of Sr 2 CuO 3 along and perpendicular to the chain direction by electron energy loss spectroscopy (EELS). 10 Peaks unique along the chain direction are considered to be the ZRS state involved transitions, while structures common in both directions are attributed to transitions localized within one plaquette. Interestingly, the strong charge transfer excitation right above the gap was found to be composed of two peaks.…”

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confidence: 99%

Optical excitations inSr2CuO3

Kim

2009

Phys. Rev. B

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We investigated excitation spectra of the one-dimensional chain compound Sr2CuO3. The small peak at 2.3 eV in the loss function turned out to correspond to the strong charge transfer transition at 1.8 eV in conductivity. It has the excitonic character expected in one dimensional extended Hubbard model of the transition from the lower Hubbard band to the Zhang-Rice singlet state. The strongest peak at 2.7 eV in the loss function is attributed to the continuum excitation of the excitonic charge transfer transition. The spectral weight sum rule is satisfied within these transitions.PACS numbers: 71.27.+a, 71.35.-y, 78.20.-e, 78.67.-n Superconducting cuprates have a CuO 2 plane in common which is composed of a two dimensional (2D) cornersharing network of CuO 4 plaquettes. The electronic property of an undoped CuO 2 plane should be metallic without strong onsite Coulomb repulsion at Cu sites, which divides the Cu d x 2 −y 2 state into two Hubbard bands of upper Hubbard band (UHB) and lower Hubbard band (LHB) opening a charge transfer gap between LHB (from a hole point of a view) and O 2p states. Charge doping changes the electronic structure of the CuO 2 plane finally giving rise to the high temperature superconductivity. It is important to understand the properties of insulating cuprates to solve the mystery of the high temperature superconductivity.Optical spectroscopy is one of fundamental tools to investigate electronic structure, which can directly measure the charge transfer gap. By absorbing light, holes in LHB can be excited to O 2p states. When a hole is introduced into the CuO 2 plane, the ground state becomes a well known Zhang-Rice singlet (ZRS) state evenly residing at surrounding O 2p orbitals. 1 Because an optical excitation is a charge conserving process, to be involved in optical excitations for the ZRS state, one CuO 4 plaquette should give a hole to a neighboring CuO 4 plaquette, which is possible in corner-sharing CuO 4 plaquette structures. Therefore, the first optical excitation crossing the charge transfer gap should be from LHB to the ZRS state in the CuO 2 plane as depicted in fig. 1. The second excitation is expected to be from LHB to nonbonding (NB) O 2p states in the CuO 2 plane, which is localized within one plaquette. Energies of these two excitations are essential to model the electronic structure of the CuO 2 plane.However, the electronic structure of insulating cuprates remains still unclear. Optical spectra of insulating cuprates of 1D and 2D corner-sharing structure show similar spectral feature of two peaks around 2 eV like the peaks A and B in fig. 2. It is clear that the lowest energy peak, which is rather sharp and has a large spectral weight in common, should be the charge transfer transition α from LHB to ZRS. But the origin of the other peak, which comes at about 0.5 eV higher, is still unclear. This peak is relatively broad and the strength varies depending on materials. It is rather small and appear as a hump-like shape in RE 2 CuO 4 (RE: rare earth ions) and Sr 2 CuO 3...

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“…High-resolution angle-resolved EELS measurements in Sr 2 CuO 3 for transversal polarization with momentum oriented in the plane of CuO 4 plaquette but perpendicular to chain direction allowed to exclude the two-center CT excitons and observe only the localized dipoleallowed CT transitions to nonbonding O 2pπ and O 2pσ orbitals with energy ≈ 2.0 eV and ≈ 5.5 eV, respectively. Comparative analysis of EELS spectra for longitudinal and transversal [4] polarizations with momentum oriented in the plane of CuO 4 plaquette allowed to elucidate the unconventional two-peak structure of the CT gap which is determined by a superposition of nearly degenerate one-center localized excitation and two-center CT excitons. The two-center nature of the most intensive low-lying CT exciton peaked at 2.6 eV is fairly well confirmed in the studies of nonlinear optical effects in Sr 2 CuO 3 .…”

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confidence: 99%

Photo-induced phase separation effect in cuprates

Moskvin¹

2005

J. Phys.: Conf. Ser.

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Evidence for Two Types of Low-Energy Charge Transfer Excitations inSr2CuO3

Cited by 47 publications

References 23 publications

Interplay ofp−dandd−dcharge transfer transitions in rare-earth perovskite manganites

Interplay ofp−dandd−dcharge transfer transitions in rare-earth perovskite manganites

Optical excitations inSr2CuO3

Photo-induced phase separation effect in cuprates

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