Optical properties of the spin-ladder compound<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>14</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>24</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>41</mml

Popović, Zdenka; Konstantinović, M.J.; Ivanov, V.A.; Khuong, OP; Gajić, R; Vietkin, A.; Moshchalkov, Victor

doi:10.1103/physrevb.62.4963

Cited by 39 publications

(60 citation statements)

References 37 publications

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“…[3][4][5][6][7] The doped cuprate series Sr 14−x Ca x Cu 24 O 41 exhibits unusual quantum magnetism, electron-phonon coupling, charge order, and superconductivity under high pressure ͑T c up to ϳ12 K at P Ͼ 3 GPa͒, and shares many unconventional properties that are also observed in the 2D cuprates. [4][5][6][7] Unlike 1D ͑Sr 2 CuO 3 or SrCuO 2 ͒ or 2D ͑La 2 CuO 4 or Nd 2 CuO 4 ͒ cuprates, the structurally incommensurate cuprate system Sr 14 Cu 24 O 41 ͑SCO͒ consists of two Cu-O structural units as stacked planes of chains and two-leg ladders. Photoemission spectroscopy, which gives a measure of the momentum-resolved band structure, is limited due to charging, cleavage, and surface issues in this compound.…”

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Dispersive collective charge modes in an incommensurately modulated cuprate Mott insulator

et al. 2007

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We report measurement of collective charge modes of insulating Sr 14 Cu 24 O 41 using inelastic resonant x-ray scattering over the complete Brillouin zone. Our results show that the intense excitation modes at the charge gap edge predominantly originate from ladder-containing planar substructures. The observed modes are found to be dispersive for momentum transfers along the "legs" ͑បQ ជ ʈ ĉ͒ but nearly localized along the "rungs" ͑បQ ជ ʈ â ͒. We show that the dispersion and peak width characteristics of the modes can be understood in the strong-coupling quantum limit ͑Hubbard U ӷ t ladder Ͼ t chain , where t is the hopping parameter͒. Quite generally, we demonstrate that the momentum tunability ͑Q ជ resolution͒ of inelastic x-ray scattering can be utilized to resolve mode contributions in multicomponent incommensurate quantum electron systems.

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Dispersive collective charge modes in an incommensurately modulated cuprate Mott insulator

et al. 2007

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“…Interestingly, in the so-called cuprate ladder systems like Sr123 or the telephone-number compounds (Sr,Ca,La) 14 Cu 24 O 41 a prominent peak in the magnetic Raman response is observed at the same energy of about 3000 cm −1 as in the two-dimensional compounds 19,20,22,23 . In contrast to the gapless longrange ordered two-dimensional compound, the quasi onedimensional two-leg ladders are known to be realizations of a gapped spin liquid 21 .…”

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Raman response of magnetic excitations in cuprate ladders and planes

et al. 2005

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An unified picture for the Raman response of magnetic excitations in cuprate spin-ladder compounds is obtained by comparing calculated two-triplon Raman line-shapes with those of the prototypical compounds SrCu2O3 (Sr123), Sr14Cu24O41 (Sr14), and La6Ca8Cu24O41 (La6Ca8). The theoretical model for the two-leg ladder contains Heisenberg exchange couplings J and J ⊥ plus an additional four-spin interaction Jcyc. Within this model Sr123 and Sr14 can be described by x := J /J ⊥ = 1.5, xcyc := Jcyc/J ⊥ = 0.2, J Sr123 ⊥ = 1130 cm −1 and J Sr14 ⊥ = 1080 cm −1 . The couplings found for La6Ca8 are x = 1.2, xcyc = 0.2, and J La6Ca8 ⊥ = 1130 cm −1 . The unexpected sharp two-triplon peak in the ladder materials compared to the undoped two-dimensional cuprates can be traced back to the anisotropy of the magnetic exchange in rung and leg direction. With the results obtained for the isotropic ladder we calculate the Raman line-shape of a two-dimensional square lattice using a toy model consisting of a vertical and a horizontal ladder. A direct comparison of these results with Raman experiments for the two-dimensional cuprates R2CuO4 (R=La,Nd), Sr2CuO2Cl2, and YBa2Cu3O 6+δ yields a good agreement for the dominating two-triplon peak. We conclude that short range quantum fluctuations are dominating the magnetic Raman response in both, ladders and planes. We discuss possible scenarios responsible for the high-energy spectral weight of the Raman line-shape, i.e. phonons, the triple-resonance and multi-particle contributions.

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“…There are several experimental realizations of spin ladders like CaV 2 O 5 , SrCu 2 O 3 and La y Ca 14−y Cu 24 O 41 rendering direct comparison between theory and experiment possible [7][8][9][10][11].…”

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Raman response in antiferromagnetic two-leg S = 1/2 Heisenberg ladders

2001

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The Raman response in the antiferromagnetic 2-leg S = 1/2 Heisenberg ladder is calculated for various couplings by continuous unitary transformations. For leg couplings above 80% of the rung coupling a characteristic 2-peak structure occurs with a point of zero intensity within the continuum. Experimental data for CaV2O5 and LayCa14−yCu24O41 are analyzed and the coupling constants are determined. Evidence is found that the Heisenberg model is not sufficient to describe cuprate ladders. We argue that a cyclic exchange term is the appropriate extension.PACS numbers: 75.40. Gb, 75.50.Ee, 75.10.Jm Strongly correlated electron systems in low dimensions are of fundamental interest due to their fascinating properties resulting from strong quantum fluctuations [1][2][3]. Important experimental insight is gained from spectroscopic measurements of such systems. The spectral densities measured yield information on the kinetics and on the interaction of the elementary excitations as well as on the matrix elements involved. Thus quantitative theoretical calculations of spectral densities are a major task in condensed matter physics. We use optimally chosen continuous unitary transformations (CUT) to map complex many-body problems to a tractable few-body problems [4]. This clear concept serves as a perfect basis to compute spectral densities of strongly correlated systems thus establishing a quantitative contact between theory and experiment [5].We will focus on optical investigations, in particular on the Raman response, of antiferromagnetic 2-leg Heisenberg ladders realizing quasi one-dimensional (1D) strongly correlated systems. There are several experimental realizations of spin ladders like CaV 2 O 5 , SrCu 2 O 3 and La y Ca 14−y Cu 24 O 41 rendering direct comparison between theory and experiment possible [7][8][9][10][11].Raman scattering measures excitations with zero change of spin and momentum. Starting at T = 0 from the S = 0 ground state the singlet excitations at zero momentum are probed. The Raman response in spin ladders was recently calculated by first order perturbation theory for spin ladders [12] and by exact diagonalization [13]. In this work, we present detailed predictions obtained from CUTs using rung triplets as elementary excitations. Our results are not resolution limited because neither finite size effects occur nor artificial broadenings are necessary.The Hamiltonian for the 2-leg Heisenberg ladder readswhere J > 0 and J ⊥ > 0 are the leg and rung couplings; the subscript i denotes the rungs and 1, 2 the two legs. At T = 0 the Raman response I(ω) is given by the retarded resolventThe observables R rung (R leg ) for magnetic light scattering in rung-rung (leg-leg) polarization read in leading order [14,15]The factors A leg 0and A rung 0 depend on the underlying microscopic electronic model. It is beyond the scope of the present work to compute them. Equally, we do not consider resonating Raman excitation processes. Results will be given in units of the factors squared.Technically, we employ a CUT...

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Optical properties of the spin-ladder compoundSr14Cu24O41

Cited by 39 publications

References 37 publications

Dispersive collective charge modes in an incommensurately modulated cuprate Mott insulator

Dispersive collective charge modes in an incommensurately modulated cuprate Mott insulator

Raman response of magnetic excitations in cuprate ladders and planes

Raman response in antiferromagnetic two-leg S = 1/2 Heisenberg ladders

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