One-dimensional Cuprates Research Articles

Influence of extended interactions on spin dynamics in one-dimensional cuprates

Influence of extended interactions on spin dynamics in one-dimensional cuprates

Signatures of the attractive interaction in spin spectra of one-dimensional cuprate chains

Identifying the minimal model for cuprates is crucial for explaining the high-Tc pairing mechanism. Recent photoemission experiments have suggested a significant near-neighbor attractive interaction V in cuprate chains, favoring pairing instability. To determine its strength, we systematically investigate the dynamical spin structure factors S(q,ω) using the density matrix renormalization group. Our analysis quantitatively reveals a notable softening in the two-spinon continuum, particularly evident in the intense spectrum at large momentum. This softening is primarily driven by the renormalization of the superexchange interaction, as determined by a comparison with the slave-boson theory. We also demonstrate the feasibility of detecting this spectral shift in thin-film samples using resonant inelastic x-ray scattering. Therefore, this provides a distinctive fingerprint for the attractive interaction, motivating future experiments to unveil essential ingredients in cuprates. Published by the American Physical Society 2024

Pseudo-transition between antiferromagnetic and charge orders in a minimal spin-pseudospin model of one-dimensional cuprates

This study rigorously investigates the phenomenon of a pseudo-transition in a minimal spin-pseudospin model, serving as a simplified model of one-dimensional cuprate chains [CuO]∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_\\infty $$\\end{document}, by making use of the transfer-matrix method. The studied spin-pseudospin model of one-dimensional cuprate chains [CuO]∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_\\infty $$\\end{document} reveals a peculiar pseudo-transition between a charged-ordered phase and an antiferromagnetic phase, which is accompanied with anomalous behavior of magnetic and thermodynamic quantities. While the entropy and short-range correlations undergo near the pseudo-transition steep continuous changes reminiscent of a discontinuous phase transition, the specific heat displays a sizable sharp peak akin to a continuous phase transition.Graphic A density plot of the specific heat of one-dimensional spin-pseudospin model of cuprate chain in the inter-site interaction versus temperature plane, which serves as a pseudo-phase diagram involving charged-ordered (CO) and antiferromagnetic (AF) phases

Spectral properties of a one-dimensional extended Hubbard model from bosonization and time-dependent variational principle: Applications to one-dimensional cuprates

Spectral properties of a one-dimensional extended Hubbard model from bosonization and time-dependent variational principle: Applications to one-dimensional cuprates

Traces of electron-phonon coupling in one-dimensional cuprates

The appearance of certain spectral features in one-dimensional (1D) cuprate materials has been attributed to a strong, extended attractive coupling between electrons. Here, using time-dependent density matrix renormalization group methods on a Hubbard-extended Holstein model, we show that extended electron-phonon (e–ph) coupling presents an obvious choice to produce such an attractive interaction that reproduces the observed spectral features and doping dependence seen in angle-resolved photoemission experiments: diminished 3kF spectral weight, prominent spectral intensity of a holon-folding branch, and the correct holon band width. While extended e–ph coupling does not qualitatively alter the ground state of the 1D system compared to the Hubbard model, it quantitatively enhances the long-range superconducting correlations and suppresses spin correlations. Such an extended e–ph interaction may be an important missing ingredient in describing the physics of the structurally similar two-dimensional high-temperature superconducting layered cuprates, which may tip the balance between intertwined orders in favor of uniform d-wave superconductivity.

Chebyshev pseudosite matrix product state approach for the spectral functions of electron-phonon coupling systems

The electron-phonon ($e$-ph) coupling system often has a large number of phonon degrees of freedom, whose spectral functions are numerically difficult to compute using matrix product state (MPS) formalisms. To solve this problem, we propose a new and practical method that combines the Chebyshev MPS and the pseudosite density matrix renormalization group (DMRG) algorithm. The Chebyshev vector is represented by a pseudosite MPS with global $U(1)$ fermion symmetry, which maps $2^{N_p}$ bosonic degrees of freedom onto $N_p$ pseudosites, each with two states. This approach can handle arbitrary $e$-ph coupling Hamiltonians where pseudosite DMRG performs efficiently. We use this method to study the spectral functions of the doped extended Hubbard-Holstein model in a regime of strong Coulomb repulsion, which has not been studied extensively before. Key features of the excitation spectra are captured at a modest computational cost. Our results show that weak extended $e$-ph couplings can increase the spectral weight of the holon-folding branch at low phonon frequencies, in agreement with angle-resolved photoemission observations on one-dimensional (1D) cuprates.

Phonon-Mediated Long-Range Attractive Interaction in One-Dimensional Cuprates.

Establishing a minimal microscopic model for cuprates is a key step towards the elucidation of a high-T_{c} mechanism. By a quantitative comparison with a recent insitu angle-resolved photoemission spectroscopy measurement in doped 1D cuprate chains, our simulation identifies a crucial contribution from long-range electron-phonon coupling beyond standard Hubbard models. Using reasonable ranges of coupling strengths and phonon energies, we obtain a strong attractive interaction between neighboring electrons, whose strength is comparable to experimental observations. Nonlocal couplings play a significant role in the mediation of neighboring interactions. Considering the structural and chemical similarity between 1D and 2D cuprate materials, this minimal model with long-range electron-phonon coupling will provide important new insights on cuprate high-T_{c} superconductivity and related quantum phases.

Augmented model captures behavior in one-dimensional cuprates

Augmented model captures behavior in one-dimensional cuprates

Charge-orbital-lattice coupling effects in theddexcitation profile of one-dimensional cuprates

We identify dd-excitations in the quasi-one dimensional compound Ca$_2$Y$_2$Cu$_5$O$_{10}$ using resonant inelastic x-ray scattering. By tuning across the Cu L$_3$-edge, we observe abrupt shifts in the dd-peak positions as a function of incident photon energy. This observation demonstrates orbital-specific coupling of the high-energy excited states of the system to the low-energy degrees of freedom. A Franck-Condon treatment of electron-lattice coupling, consistent with other measurements in this compound, reproduces these shifts, explains the Gaussian lineshapes, and highlights charge-orbital-lattice renormalization in the high energy d-manifold.

Synthesis and Characterization of the One-dimensional Cuprate Sr2CuO3 Nanoparticles Prepared by Modified Sol-gel Method

AbstractA modified sol-gel synthesis route has been used to prepare the fine homogeneous powder of Sr2CuO3 ceramic using strontium nitrate, copper nitrate, diethylene glycol monobutyl ether and citric acid. XRD patterns showed that the temperature of forming Sr2CuO3 is about 900°C and single phase of Sr2CuO3 with high purity obtains at 950°C. Influence of concentration of citric acid on the structure of prepared materials was investigated by SEM images.

High-resolution resonant inelastic X-ray scattering with soft X-rays at the ADRESS beamline of the Swiss light source: Instrumental developments and scientific highlights

The experimental development of the resonant inelastic X-ray scattering (RIXS) technique in the soft X-ray energy range has been tremendous during the last years. The ADRESS beamline at the Paul Scherrer Institut in Switzerland and its RIXS spectrometer SAXES has boosted the scientific capabilities with soft X-ray RIXS. Increased resolving power above 10,000 and the possibility to rotate the spectrometer to different scattering geometries allows analyzing the collective behavior of charge, orbital and spin excitations by assessing their momentum dependence. Focus of most projects at this facility lies in the investigation of low- and medium-energy excitations in correlated electron materials. In addition ADRESS has also been used for RIXS investigations on molecules in the liquid and gaseous phase. This review reports on the recent extension of the optics of the SAXES RIXS spectrometer with an additional grating optimized for the spectral range from ca. 400 to 700eV. Furthermore, the scientific opportunities emerging from ADRESS are highlighted in RIXS studies on quasi one-dimensional cuprates, oxide heterostructures and a weakly correlated broad band material.

Doping dependence of magnetic excitations of one-dimensional cuprates as probed by resonant inelastic x-ray scattering

We study the dynamical, momentum dependent two- and four-spin response functions in doped and undoped 1D cuprates, as probed by resonant inelastic x-ray scattering, using an exact numerical diagonalization procedure. In the undoped $t-J$ system the four-spin response vanishes at $\pi$, whereas the two-spin correlator is peaked around $\pi/2$, with generally larger spectral weight. Upon doping spectra tend to soften and broaden, with a transfer of spectral weight towards higher energy. However, the total spectral weight and average peak position of either response are only weakly affected by doping up to a concentration of 1/8. Only the two-spin response at $\pi$ changes strongly, with a large reduction of spectral weight and enhancement of excitation energy. At other momenta the higher-energy, generic features of the magnetic response are robust against doping. It signals the presence of strong short-range antiferromagnetic correlations, even after doping mobile holes into the system. We expect this to hold also in higher dimensions.

Effect of covalent bonding on magnetism and the missing neutron intensity in copper oxide compounds

The importance of covalent bonding for the magnetism of 3d metal complexes was first noted by Pauling in 1931. His point became moot, however, with the success of the ionic picture of Van Vleck, where ligands influence magnetic electrons of 3d ions mainly through electrostatic fields. Anderson's theory of spin superexchange later established that covalency is at the heart of cooperative magnetism in insulators, but its energy scale was believed to be small compared to other inter-ionic interactions and therefore it was considered a small perturbation of the ionic picture. This assertion fails dramatically in copper oxides, which came to prominence following the discovery of high critical temperature superconductors (HTSC). Magnetic interactions in cuprates are remarkably strong and are often considered the origin of the unusually high superconducting transition temperature, Tc. Here we report a detailed survey of magnetic excitations in the one-dimensional cuprate Sr2CuO3 using inelastic neutron scattering (INS). We show that although the experimental dynamical spin structure factor is well described by the model S=1/2 nearest-neighbour Heisenberg Hamiltonian typically used for cuprates, the magnetic intensity is modified dramatically by strong hybridization of Cu 3d states with O p states, showing that the ionic picture of localized 3d Heisenberg spin magnetism is grossly inadequate. Our findings provide a natural explanation for the puzzle of the missing INS magnetic intensity in cuprates and have profound implications for understanding current and future experimental data on these materials.

Effect of electron–phonon interaction on optical response in one-dimensional cuprates

We examine the single-particle excitation and linear optical absorption spectra in the one-dimensional (1D) extended Hubbard–Holstein model. We perform dynamical density matrix renormalization group calculations with use of pseudo-site representation of phonons. We focus on the interplay among phonons and elementary excitations in 1D Mott insulators. The excitations in the Mott insulators are easily modified by the phonons. We discuss implications of the present results in light of spectroscopic measurements in 1D cuprates.

Electronic structure and magnetic properties of the spin-1∕2Heisenberg magnetBi2CuO4

The electronic and magnetic structure of the spin-$1∕2$ magnet ${\mathrm{Bi}}_{2}\mathrm{Cu}{\mathrm{O}}_{4}$ is investigated by band structure calculations within the local (spin) density approximation [L(S)DA]. The insulating compound shows a complex of narrow, half-filled antibonding bands within the LDA, indicating the importance of strong on-site correlation effects. To describe the lowest-lying excitations, the strong Coulomb correlations have been taken into account by a subsequent mapping of the LDA band structure onto a tight-binding model and via an extended Hubbard model onto an extended Heisenberg model. Alternatively, the leading exchange interactions have been estimated applying the $\mathrm{LSDA}+U$ method for different spin configurations in magnetic supercells. Using our estimated exchange constants, we calculated the spin wave dispersion and the N\'eel temperature within the random phase approximation. The calculated properties are in good agreement with experimental data, suggesting that the magnetic ground state of ${\mathrm{Bi}}_{2}\mathrm{Cu}{\mathrm{O}}_{4}$ is governed by the antiferromagnetic interaction between the structural one-dimensional cuprate chains.

Excited state nonlinear optics of quasi-one-dimensional Mott-Hubbard insulators

Ground as well as excited state nonlinear optical properties of one-dimensional Mott-Hubbard insulators are discussed in detail. One-dimensional strongly correlated materials are predicted to have several orders of magnitude larger excited state optical nonlinearities in comparison to that from the ground state. Unlike $\ensuremath{\pi}$-conjugated polymers and other classes of one-dimensional systems, strongly correlated materials such as ${\mathrm{Sr}}_{2}\mathrm{Cu}{\mathrm{O}}_{3}$, halogen-bridged Ni compounds, etc., have excited one- and two-photon allowed states almost energetically degenerate, which leads to order(s)-of-magnitude larger dipole coupling between them in comparison to that between the ground and optical states. This causes several orders of magnitude enhancement in the optical nonlinearities obtained from the first two-photon state in the wavelength region suitable for terahertz communications. Our results and conclusions are based on exact numerical calculations of the extended Hubbard model suitable for strongly correlated systems. We argue based on theoretical as well as available experimental data that one-dimensional cuprates would be a good source of terahertz radiation, to be experimentally verified. We also discuss in detail ground state nonlinear properties such as third-harmonic generation, two-photon absorption, and electroabsorption from the theoretical model and compare with experiments. Theoretical calculations of excited state nonlinearities of some $\ensuremath{\pi}$-conjugated polymers are also presented for comparison.

Theory of resonant X-ray emission spectra for high Tc cuprates

Resonant X-ray emission spectroscopy (RXES) is a powerful tool in the study of electronic states of various materials. In this paper, we report two recent topics of RXES for high T c related cuprates: Cu Kα RXES of La 2CuO 4 and Cu 1s → 4p → 1s RXES of one-dimensional cuprates. We first show from both experimental and theoretical studies that the Cu Kα RXES in La 2CuO 4 is extremely sensitive to fine structures in the pre-edge region of the Cu 1s X-ray absorption. Calculations combining the Cu 4p density of states obtained by ab initio method with a many-body cluster model including a single Cu site show remarkable agreement with experiment. In particular, we show that an extremely weak off-site Cu 1s → 3d dipole transition-mediated by Cu 4p–O 2p and O 2p–Cu 3d hybridizations can also be clearly detected by the Cu Kα RXES. Then we give theoretical calculations of the Cu 1s → 4p → 1s RXES spectra for one-dimensional Cu 6O 18 cluster model. The results indicate that the RXES spectra are sensitive to the energy dispersion of a pair excitation of an upper-Hubbard band electron and a Zhang–Rice-singlet band hole, the excitation of local antibonding state between 3d 9 and 3d 10 L configurations, and the crystal field excitation. The role of the Cu 3d orbital degeneracy is also discussed.

CopperKand OxygenKResonant Inelastic X-ray Scattering of One-Dimensional Cuprates

Resonant inelastic X-ray scattering (RIXS) using the Cu K shell of one-dimensional cuprates is compared with that using the O K shell on the basis of numerically-exact diagonalization calculations applied for a finite-size cluster model. Particular attention is paid to the effects of Cu 3 d orbital degeneracy on the Cu K RIXS and the incident photon energy dependence of the Cu K RIXS. Inclusion of the Cu 3 d (3 z 2 - r 2 ) orbital results in the d d excitation in the Cu K RIXS, which is in accordance with the O K RIXS. However the excitation mechanism differs for the Cu K RIXS and O K RIXS. The d d excitation in the Cu K RIXS is caused through the mixing between the Zhang–Rice singlet (ZRS) and Cu 3 d (3 z 2 - r 2 ) bands, while it is mainly caused by the optical dipole transition process in the case of O K RIXS. Moreover, mixing between the ZRS and Cu 3 d (3 z 2 - r 2 ) bands induces new structures, whose binding energy is higher than that of the structure due to electron–hole pair excitations from the Z...

High-throughput characterization of linear and nonlinear optical properties in composition-spread (Sr,Ca) 2CuO 3 thin-films

We have constructed a high-throughput spectrometer and a nonlinear optical tester used for the characterization of combinatorial thin-film libraries. The optical spectrometer consists of a multi-channel detector and an automated bidimensional translation stage. The transmission spectrum of an area of 0.5 mm×2 mm can be measured for a wavelength range of 280–900 nm. Our nonlinear optical tester uses a compact mode-locked fiber-laser as an excitation source. The laser beam is focused by a graded index lens, the fundamental light is filtered out, and the third-harmonic (TH) light is detected by a photomultiplier. The data collection and the motion of the stepping motor-driven stage are synchronized. Typical measurement time for a composition-spread thin-film is 5 min. A demonstration is shown for a composition-spread thin-film of one-dimensional cuprate (Sr x Ca 1− x ) 2CuO 3 with gigantic third-order optical nonlinearity.

Modulated Structure of the Composite Crystal Ca0.83CuO2

We have determined the crystal structure of the quasi one-dimensional cuprate Ca0.83CuO2, known as Ca4Cu5O10, etc., by a superspace group approach. The compound consists of two interpenetrating subsystems of CuO2 chains and Ca atoms. Structural parameters were refined with a superspace group of F2/m(1+α 0 γ)0s using powder X-ray and neutron diffraction data. Lattice parameters were refined to be a1=2.8043(2) Å, b=6.3179(2) Å, c1=10.5744(5) Å, and β1=90.10(1)° for the [CuO2] subsystem and a2=3.3652(2) Å, b=6.3179(2) Å, c2=10.5893(5) Å, and β2=93.04(1)° for the [Ca] subsystem. Remarkable displacive modulation of the O and Ca atom sites is observed parallel to the b-axis and the c-axis, respectively. On the other hand, the Cu atom sites deviate mainly in the a direction to yield a periodic fluctuation between the nearest Cu–Cu distances. The Ca atoms suitably sit in the center of the modulated O6 octahedra.