Crossover of the high-energy spin fluctuations from collective triplons to localized magnetic excitations in doped Sr14-xCaxCu24O41 cuprate ladders
Y. Tseng, J. Thomas, W. Zhang, E. Paris, P. Puphal, R. Bag, G. Deng, T. C. Asmara, V. N. Strocov, S. Singh, E. Pomjakushina, U. Kumar, A. Nocera, H. M. Rønnow, … 展开作者
Y. Tseng, J. Thomas, W. Zhang, E. Paris, P. Puphal, R. Bag, G. Deng, T. C. Asmara, V. N. Strocov, S. Singh, E. Pomjakushina, U. Kumar, A. Nocera, H. M. Rønnow, S. Johnston, T. Schmitt
We studied the magnetic excitations in the quasi-one-dimensional (q-1D) ladder subsystem of Sr_(14-x) Ca_x Cu_24 O_41(SCCO) using Cu L_3-edge resonant inelastic X-ray scattering (RIXS). By comparing momentum-resolved RIXS spectra with (x=12.2) and without (x=0) high Ca content, we track the evolution of the magnetic excitations from collective two-triplon (2T) excitations (x=0) to weakly-dispersive gapped modes at an energy of 280 meV (x=12.2). Density matrix renormalization group (DMRG) calculations of the RIXS response in the doped ladders suggest that the flat magnetic dispersion and damped excitation profile observed at x=12.2 originates from enhanced hole localization. This interpretation is supported by polarization-dependent RIXS measurements, where we disentangle the spin-conserving ΔS=0 scattering from the predominant ΔS=1 spin-flip signal in the RIXS spectra. The results show that the low-energy weight in the ΔS=0 channel is depleted when Sr is replaced by Ca, consistent with a reduced carrier mobility. Our results demonstrate that off-ladder impurities can affect both the low-energy magnetic excitations and superconducting correlations in the CuO_4 plaquettes. Finally, our study characterizes the magnetic and charge fluctuations in the phase from which superconductivity emerges in SCCO at elevated pressures.
Based on a two-dimensional model of coupled two-leg spin ladders, we derive a unified picture of recent neutron scattering data of stripe-ordered La_(15/8)Ba_(1/8)CuO_4, namely of the low-energy magnons around the superstructure satellites and of the triplon excitations at higher energies. The resonance peak at the antiferromagnetic wave vector Q_AF in the stripe-ordered phase corresponds to a saddle point in the dispersion of the magnetic excitations. Quantitative agreement with the neutron data is obtained for J= 130-160 meV and J_cyc/J = 0.2-0.25.
This article summarizes and extends the recent developments in the microscopic modeling of the magnetic excitations in cuprate two-leg ladder systems. The microscopic Hamiltonian comprises dominant Heisenberg exchange terms plus an additional four-spin interaction which is about five times smaller. We give an overview over the relevant energies like the one-triplon dispersion, the energies of two-triplon bound states and the positions of multi-triplon continua and over relevant spectral properties like spectral weights and spectral densities in the parameter regime appropriate for cuprate syst…
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_parallel and J_perp plus an additional four-spin interaction J_cyc. Within this model Sr123 and Sr14 can be described by x:=J_parallel/J_perp=1.5, x_cyc:=J_cyc/J_perp=0.2, J_perp^Sr123=1130 cm^-1 and J_perp^Sr14=1080 cm^-1. The couplings found…
We explore the properties of magnetic excitations on the trellis lattice which is relevant for the so-called telephone-number compounds A$_{14}$Cu$_{24}$O$_{41}$ and the system SrCu$_2$O$_3$. The trellis lattice consists of two-leg ladders which are coupled in a strongly frustrated fashion. We use the effective model obtained for a single two-leg spin ladder to calculate the two-dimensional one-triplon dispersion and the corresponding one-triplon contribution to the dynamical structure factor. Special attention is laid on signatures of the frustrating inter-ladder magnetic exchange. A detailed…
We construct a 2-leg ladder model of an Fe-pnictide superconductor and discuss its properties and relationship with the familiar 2-leg cuprate model. Our results suggest that the underlying pairing mechanism for the Fe-pnictide superconductors is similar to that for the cuprates.
Within the t-J ladder model, superconductivity with a modified d-wave symmetry in doped two-leg ladder cuprates is investigated based on the kinetic energy driven superconducting mechanism. It is shown that the spin-liquid ground-state at the half-filling evolves into the superconducting ground-state upon doping. In analogy to the doping dependence of the superconducting transition temperature in the planar cuprate superconductors, the superconducting transition temperature in doped two-leg ladder cuprates increases with increasing doping in the underdoped regime, and reaches a maximum in the …
Within the kinetic energy driven superconducting mechanism, the effect of the pressure on superconductivity in doped two-leg ladder cuprates is studied. It is shown that the superconducting transition temperature in doped two-leg ladder cuprate superconductors increases with increasing pressure in the underpressure regime, and reaches a maximum in the optimal pressure, then decreases in the overpressure regime. This domed shape of the pressure dependence of the superconducting transition temperature is similar to that of the pressure dependence of the longitudinal part of the superconducting g…
The ladder compound Sr$_{14}$Cu$_{24}$O$_{41}$ is of interest both as a quasi-one-dimensional analog of the superconducting cuprates and as a superconductor in its own right when Sr is substituted by Ca. In order to model resonant inelastic x-ray scattering (RIXS) spectra for this compound, we investigate the simpler SrCu$_{2}$O$_{3}$ system in which the crystal structure contains very similar ladder planes. We approximate the LDA dispersion of SrCu$_{2}$O$_{3}$ by a Cu only two-band tight-binding model. Strong correlation effects are incorporated by assuming an anti-ferromagnetic ground state…
Within the two-leg $t$-J ladder, the spin dynamics of the pressure-induced two-leg ladder cuprate superconductor Sr$_{14-x}$Ca$_{x}$Cu$_{24}$O$_{41}$ is studied based on the kinetic energy driven superconducting mechanism. It is shown that in the pressure-induced superconducting state, the incommensurate spin correlation appears in the underpressure regime, while the commensurate spin fluctuation emerges in the optimal pressure and overpressure regimes. In particular, the spin-lattice relaxation time is dominated by a temperature linear dependence term at low temperature followed by a peak dev…
Correlated-electron theories of superconductivity in layered cuprates often start from the premise of a gapped spin-liquid phase proximate to the superconducting state. This assumption is justified based on analytical and numerical demonstrations of a superconducting Luther-Emery phase in the doped 2-leg one-band Hubbard ladder, and the perceived analogy between coupled ladders and the two dimensional CuO2 layer. We demonstrate from accurate density matrix renormalization group studies the absence of the superconducting Luther-Emery phase in the doped 2-leg three-band ladder consisting of both…
The enigmatic scaling behaviour of the normal state properties of the high Tc cuprates has been explained by assuming that a crossover from the two- dimensional Heisenberg (2D-H) to the one-dimensional spin ladder (1D-SL) regime takes place at temperature T=T*. For T<T* stripe formation results in the quantum 1D transport with the characteristic inelastic length L_phi being fully controlled by the magnetic correlation length xi_m of the even-chain SL, whereas for T> T* the 2D quantum transport is realized with L_ϕgoverned by the 2D-H correlations L_phi=xi_m=exp(J/T)$. Therefore, the pseudogap …
According to the celebrated Onsagar-Lifshitz paradigm, the observation of Shubnikov de-Haas and de-Haas van Alphen (SdHvA) oscillations is an indication of the presence of `closed' orbit Fermi surface in the bulk. We present a real-space based calculation of SdHvA oscillations in generalized quasi-one-dimensional lattices by relaxing the quasi-classical approximations embedded in this decades old Onsagar-Lifshitz paradigm. We find that sizable quantum oscillation can arise from `open' Fermi surfaces as long as cyclotron orbits can form in real-space with finite, but not necessarily equal, elec…
A light-induced charge order mode in a metastable cuprate ladder
Harvard University（哈佛大学）；Emory University（埃默里大学）；Brookhaven National Laboratory（布鲁克海文国家实验室）；University of Notre Dame（圣母大学）；Paul Scherrer Institute（保罗谢勒研究所）
We study the superconductivity in the three-dimensional multiband d-p model, in which a Cu$_2$O$_3$-ladder layer and a CuO$_2$-chain layer are alternately stacked, as a model of the superconducting spin-chain ladder cuprate. $p_z$-Wave-like triplet superconductivity is found to be the most stable, and its dependence on interlayer coupling can explain the superconducting transition temperature dependence on pressure in real superconducting spin-chain ladder cuprates. The superconductivity may be enhanced if hole transfer from the chain layer to the ladder layer can be promoted beyond the typica…
Exact Diagonalization calculations are presented for the t-J model in the presence of a uniform magnetic field. Results for 2xL ladders (L=8,10,12) and 4x4 square clusters with 1 and 2 holes indicate that the diamagnetic response to a perpendicular magnetic field tends to induce a spin liquid state in the spin background. The zero-field spin liquid state of a two-leg ladder is reinforced by the magnetic field: a considerable increase of rung antiferromagnetic correlations is observed for J/t up to 0.6, for 1 and 2 holes. Pair-breaking is also clearly observed in the ladders and seems to be ass…
We report the first measurement of collective charge modes of insulating Sr14Cu24O41 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 the ladder-containing planar substructures. The observed ladder modes (E vs. Q) are found to be dispersive for momentum transfers along the "legs" but nearly localized along the "rungs". Dispersion and peakwidth characteristics are similar to the charge spectrum of 1D Mott insulators, and we show that our results can be understood in …
We theoretically study the effect of uniaxial deformation of ladder-type cuprate superconductors. Model construction based on first principles calculation shows that the rung-to-leg ratio of the nearest neighbor hoppings counterintuitively increases when the lattice is compressed in the longitudinal (leg) direction. This leads to an enhancement of the superconducting transition temperature, which intuitively is expected when compressed in the rung direction. Such a trend is traced back to the on-site hybridization between Cu$4s$ and Cu$d_{x^2-y^2}$ orbitals, which varies and changes sign upon …
The formation of domains comprising alternating 'hole rich' and 'hole poor' ladders recently observed by Scanning Tunneling Microscopy by Kohsaka et al., on lightly hole doped cuprates, is interpreted in terms of an attractive mechanism which favors the presence of doped holes on Cu sites located each on one side of an oxygen atom. This mechanism leads to a geometrical pattern of alternating hole-rich and hole-poor ladders with a periodicity equal to 4 times the lattice spacing in the CuO plane, as observed experimentally. To cite this article: G. Deutscher, P.-G. de Gennes, C. R. Physique 8 (…
The magnetic excitations in the stripe phase of high-T_c superconductors are investigated in a model of spin ladders which are effectively coupled via charged stripes. Starting from the effective single-triplon model for the isolated spin ladder, the quasi-one-dimensional spin system can be described straightforwardly. Very good agreement is obtained with recent neutron scattering data on La_(15/8)Ba_(1/8)CuO_4 (no spin gap) and YBa_2Cu_3O_(6.6) (gapped). The signature of quasi-one-dimensional spin physics in a single-domain stripe phase is predicted.
The tendencies to phase-separation and stripe formation of the t-J model on planes and four-leg ladders have been here reexamined including hole hopping terms t', t'' beyond nearest-neighbor sites. The motivation for this study is the growing evidence that such terms are needed for a quantitative description of the cuprates. Using a variety of computational techniques it is concluded that the stripe tendencies considerably weaken when experimentally realistic t'<0, t''>0 for hole-doped cuprates are considered. However, a small t'>0 actually enhances the stripe formation.
We study a model of the quantum critical point of cuprates associated with the "circulating current" order parameter proposed by Varma. An effective action of the order parameter in the quantum disordered phase is derived using functional integral method, and the physical properties of the normal state are studied based on the action. The results derived within the ladder approximation indicate that the system is like Fermi liquid near the quantum critical point and in disordered regime up to minor corrections. This implies that the suggested marginal Fermi liquid behavior induced by the circu…
Pressure-induced superconductivity was studied for a spin-ladder cuprate Sr$_2$Ca$_{12}$Cu$_{24}$O$_{41}$ using nuclear magnetic resonance (NMR) under pressures up to the optimal pressure 3.8 GPa. Pressure application leads to a transitional change from a spin-gapped state to a Fermi-liquid state at temperatures higher than $T_c$. The relaxation rate $1/T_1$ shows activated-type behavior at an onset pressure, whereas Korringa-like behavior becomes predominant at the optimal pressure, suggesting that an increase in the density of states (DOS) at the Fermi energy leads to enhancement of $T_c$. N…
The spin dynamics of a doped 2-leg spin ladder is investigated by numerical techniques. We show that a hole pair-magnon boundstate evolves at finite hole doping into a sharp magnetic excitation below the two-particle continuum. This is supported by a field theory argument based on a SO(6)-symmetric ladder. Similarities and differences with the resonant mode of the high-T$_c$ cuprates are discussed.
LaCuO_2.5 is a system of coupled, two-chain, cuprate ladders which may be doped systematically by Sr substitution. Motivated by the recent synthesis of single crystals, we investigate theoretically the possibility of superconductivity in this compound. We use a model of spin fluctuation-mediated superconductivity, where the pairing potential is strongly peaked at πin the ladder direction. We solve the coupled gap equations on the bonding and antibonding ladder bands to find superconducting solutions across the range of doping, and discuss their relevance to the real material.
We provide, for the first time, in a doped strongly correlated system (two-leg ladder), a controlled theoretical demonstration of the existence of a state in which long-range ordered orbital currents are arranged in a staggered pattern,coexisting with a charge density wave. The method used is the highly accurate density matrix renormalization group technique.This brings us closer to recent proposals that this order is realized in the enigmatic pseudogap phase of the cuprate high temperature superconductors.
We study a one-dimensional electron liquid coupled by a weak spin-exchange interaction to an antiferromagnetic spin-S ladder with n legs. A perturbative renormalization group analysis in the semiclassical limit reveals the opening of a spin gap, driven by the local magnetic correlations on the ladder. The effect, which we argue is present for any gapful ladder or gapless ladder with $nS\gg 1$, is enhanced by the repulsive interaction among the conduction electrons but is insensitive to the sign of the spin exchange interaction with the ladder. Possible implications for the striped phases of th…
The hole-doped antiferromagnetic spin-1/2 two-leg ladder is an important model system for the high-$T_c$ superconductors based on cuprates. Using the technique of self-similar continuous unitary transformations we derive effective Hamiltonians for the charge motion in these ladders. The key advantage of this technique is that it provides effective models explicitly in the thermodynamic limit. A real space restriction of the generator of the transformation allows us to explore the experimentally relevant parameter space. From the effective Hamiltonians we calculate the dispersions for single ho…
Raman measurements in the 1.5 - 20 cm-1 energy range were performed on single crystals of Sr_{14-x}Ca_xCu_{24}O_{41}. A quasielastic scattering peak (QEP) which softens with cooling is observed in the polarization parallel to the ladder direction for samples with x = 0, 8 and 12. The QEP is a Raman fingerprint of pinned collective density wave excitations screened by uncondensed carriers. Our results suggest that transport in metallic samples, which is similar to transport in underdoped high-T_c cuprates, is driven by a collective electronic response.
The ground state of the t-t'-J ladder with four legs favors a striped charge distribution for the parameters corresponding to hole-doped cuprate superconductors. We investigate the dynamical spin and charge structure factors of the model by using the dynamical density matrix renormalization group (DMRG) and clarify the influence of the stripe on the structure factors. The dynamical charge structure factor along the momentum direction from q=(0,0) to (pi,0) clearly shows low-energy excitations corresponding to the stripe order in hole doping. On the other hand, the stripe order weakens in elect…
The temperature dependence of the resistivity r(T) of the novel Sr2.5Ca11.5Cu24O41 ladder compound under hydrostatic pressure of up to 8 GPa has been explained by assuming that the relevant length scale for electrical transport is given by the magnetic correlation length related to the opening of a spin-gap in a 1D even-chain spin-ladder (1D-SL). The pressure dependence of the gap was extracted by applying this model to r(T) data obtained at different pressures. The r(T) dependence of the underdoped cuprate YBa2Cu4O8 demonstrates a remarkable scaling with the r(T) of the 1D-SL compound Sr2.5Ca…
The nature of the interplay between superconductivity and magnetism in the cuprates remains one of the fundamental unsolved problems in high temperature superconductivity. Whether and how these two phenomena are interdependent is perhaps most sharply seen in the stripe phases of various copper-oxide materials. These phases, involving a mixture of spin and charge density waves, do not yet admit a complete, overarching theoretical treatment. However aspects of this problem can be analyzed. In this work, we focus on the magnetic side of stripe physics. To this end, we study a simple model of a st…
We report studies of the electronic structure and elementary excitations of doped and undoped cuprate chains, ladders and planes. Using high energy spectroscopies such as x-ray absorption, core level photoemission and angle resolved photoemission spectroscopy, important information regarding the charge distribution and hole dynamics can be obtained. The comparison of the experimental data with suitable theoretical models sets constraints on the parameters entering into the model calculations, and offers insight into the important physical quantities governing the electronic structure of these …
We introduce a generic Froehlich-Coulomb model of the oxides, which also includes infinite on-site (Hubbard) repulsion, and describe a simple analytical method of solving the multi-polaron problem in complex lattice structures. Two particular lattices, a zig-zag ladder and a perovskite layer, are studied. We find that depending on the relative strength of the Froehlich and Coulomb interactions these systems are either polaronic Fermi (or Luttinger)-liquids, bipolaronic superconductors, or charge segregated insulators. In the superconducting phase the carriers are superlight mobile bipolarons. …
In the nested limit of the spin-fermion model for the cuprates, one-dimensional physics in the form of half-filled two-leg ladders emerges. We show that the renormalization group flow of the corresponding ladder is towards the d-Mott phase, a gapped spin-liquid with short-ranged d-wave pairing correlations, and reveals an intermediate SO(5)$\times$SO(3) symmetry. We use the results of the renormalization group in combination with a memory-function approach to calculate the optical conductivity of the spin-fermion model in the high-frequency regime, where processes within the hot spot region do…
Half-filled two-leg Hubbard ladders have spin-gapped short-range antiferromagnetic correlations while three-leg ladders have power law antoferromagnetic correlations, and both systems have d_{x^2-y^2}-power law pairing correlations when they are doped. Thus these ladders exhibit some of the phenomenology seen in the layered cuprates. Here we report results for half-filled frustrated Hubbard ladders, based upon ladder segments taken from a tight-binding model of kappa-BEDT-TTF. Although these ladders are half-filled, varying the degree of frustration can drive them across an insulator-metal tra…
We investigate the physics of frustrated 3-leg Hubbard ladders in the band limit, when hopping across the ladder's rungs (t$_{\perp}$) is of the same order as hopping along them (t) much greater than the onsite Coulomb repulsion (U). We show that this model exhibits a striking electron-hole asymmetry close to half-filling: the hole-doped system at low temperatures develops a Resonating Valence Bond (RVB)-like d-wave gap (pseudogap close to ($π$,0)) coinciding with gapless nodal excitations (nodal liquid); in contrast, the electron-doped system is seen to develop a Mott gap at the nodes, whilst…
We propose a model for a spatially modulated collective state of superconducting cuprates in which the electronic properties vary locally in space. In this model the regions of higher hole density (called stripes) are described as Luttinger liquids and the regions of lower density (antiferromagnetic ladders) as an interacting bosonic gas of d$_{x^2-y^2}$ hole pairs. We show that the transition to the superconducting state is topological and driven by decay processes among these elementary excitations in the presence of vibrations.
The spin of the neutron allows neutron scattering to reveal the magnetic structure and dynamics of materials over nanometre length scales and picosecond timescales. Neutron scattering is particularly in demand in order to understand high-temperature superconductors, which lie close to magnetically ordered phases, and highly correlated metals with giant effective fermion masses, which lie close to magnetic order or pass through a mysterious phase of hidden order before becoming superconducting. Neutron scattering also is the probe of choice for revealing new phases of matter and new particles, …
We study the magnetic and charge dynamical response of a Hubbard model in a two-leg ladder geometry using the density matrix renormalization group (DMRG) method and the random phase approximation within the fluctuation-exchange approximation (RPA+FLEX). Our calculations reveal that RPA+FLEX can capture the main features of the magnetic response from weak up to intermediate Hubbard repulsion for doped ladders, when compared with the numerically exact DMRG results. However, while at weak Hubbard repulsion both the spin and charge spectra can be understood in terms of weakly-interacting electron-…
We investigate the physical consequences of orbital current patterns (OCP) in doped two-leg Cu-O Hubbard ladders. The internal symmetry of the pattern, in the case of the ladder structure, differs slightly from that suggested so far for cuprates. We focus on this OCP and look for measurable signatures of its existence. We compute the magnetic field produced by the OCP at each lattice site, and estimate its value in view of a possible experimental detection. Using a renormalization group (RG) analysis, we determine the changes that are caused by the SU(2) spin-rotational symmetry breaking which…
We solve the problem of $N$ non magnetic impurities in the staggered flux phase of the Heisenberg model which we assume to be a good mean-field approximation for the spin-gap phase of the cuprates. The density of states is evaluated exactly in the unitary limit and is porportional to $1/\left (ω\ln^2(|ω|/D))$, in analogy with the 1D case of doped spin-Peierls and two-leg ladders compounds. We argue that the system exhibits a quasi long-range order at T=0 with instantaneous spin-spin correlations decreasing as $n_i/ \ln^2\left (n_i R_{ij})$ for large distances $R_{ij}$ and we predict enhanced l…
We probed spin-spin correlations up to 725 K with 63Cu NQR in the S= 1/2 three-leg ladder Sr2Cu3O5. We present experimental evidence that below 300 K, weak inter-ladder coupling causes dimensional crossover of the spin-spin correlation length ξfrom quasi-1d (ξ~ 1/T) to anisotropic 2d regime (ξ\~ exp[2πρ_{s}/T], where 2πρ_{s} = 290 +/- 30 K is the effective spin stiffness). This is the first experimental verification of the renormalized classical behavior of the anisotropic non-linear sigma model in 2d, which has been recently proposed for the striped phase in high T_{c} cuprates.
We discuss the phase coherence which emanates from the ladder-like proximity effect between a ``weak superconductor'' with preformed bosonic pairs (here, a single-chain Luther-Emery liquid with superconducting correlations that decay approximately as $x^{-1}$) and a Fermi gas with unpaired fermions. Carefully studying tunneling mechanism(s), we show that the boson-mediated Cooper pairing between remaining unpaired electrons results in a quasi long-range superconductivity: Superconducting correlations decay very slowly as $x^{-η}$ with $η\approx 1/2$. This process is reminiscent of the coupling…
Discovery of new high TC superconductors, with TC > 23 K, continues to be challenging. We have doubled the existing TC of single crystal Sr3Ca11Cu24O41, a spin ladder cuprate, from 12K to 24K, using a gentle uniaxial pressure ~ 0.06 GPa. In contrast, earlier works used a nearly 100 times larger hydrostatic pressure 5 GPa, only to reach a maximum TC ~ 12K. Our work exposes large and nearly equal, but opposing contributions to changes in TC, arising from compressions along and perpendicular to ladder planes, in hydrostatic pressure experiments. In our resistivity measurements, uniaxial pressure …
We discuss the magnetic excitations of well-ordered stripe and checkerboard phases, including the high energy magnetic excitations of recent interest and possible connections to the "resonance peak" in cuprate superconductors. Using a suitably parametrized Heisenberg model and spin wave theory, we study a variety of magnetically ordered configurations, including vertical and diagonal site- and bond-centered stripes and simple checkerboards. We calculate the expected neutron scattering intensities as a function of energy and momentum. At zero frequency, the satellite peaks of even square-wave s…
Motivated by recent experimental progress on iron-based ladder compounds, we study the doped two-orbital Hubbard model for the two-leg ladder BaFe$_2$S$_3$. The model is constructed by using {\it ab initio} hopping parameters and the ground state properties are investigated using the density matrix renormalization group method. We show that the $(π,0)$ magnetic ordering at half-filling, with ferromagnetic rungs and antiferromagnetic legs, becomes incommensurate upon hole doping. Moreover, depending on the strength of the Hubbard $U$ coupling, other magnetic patterns, such as $(0,π)$, are also …
The electronic structure and the single-particle spectral density of a stripe array formed by ladder-like domain walls (DWs) and by antiferromagnetic (AF) domains of width 2 lattice spacings are computed and compared with ARPES spectra from some doped cuprates belonging to the 214 family of compounds. We assume that bond order is formed on legs in DWs and that the phase of the sublattice magnetization changes by Pi across each DW. The intensity map plotted in the coordination frame momentum-energy reproduces quite well the ARPES spectra obtained at the doping level of 15%. We consider this agr…
Understanding the electron pairing in hole-doped cuprate superconductors has been a challenge, in particular because the "normal" state from which it evolves is unprecedented. Now, after three and a half decades of research, involving a wide range of experimental characterizations, it is possible to delineate a clear and consistent cuprate story. It starts with doping holes into a charge-transfer insulator, resulting in in-gap states. These states exhibit a pseudogap resulting from the competition between antiferromagnetic superexchange $J$ between nearest-neighbor Cu atoms (a real-space inter…
Based on three general guiding principles, i.e., no double occupancy constraint, accurate description of antiferromagnetism at half-filling, and the precise sign structure of the $t$-$J$ model, a new ground state wave function has been constructed recently [Weng, New J. Phys. 13, 103039 (2011)]. In this paper, we specifically study such kind of variational ground state for the one-hole-doped anisotropic two-leg $t$-$J$ ladder using variational Monte Carlo (VMC) method. The results are then systematically compared with those recently obtained by density matrix renormalization group (DMRG) simul…
Hole doping into a correlated antiferromagnet leads to topological stripe correlations, involving charge stripes that separate antiferromagnetic spin stripes of opposite phase. Topological spin stripe order causes the spin degrees of freedom within the charge stripes to feel a geometric frustration with their environment. In the case of cuprates, where the charge stripes have the character of a hole-doped two-leg spin ladder, with corresponding pairing correlations. Anti-phase Josephson coupling across the spin stripes can lead to pair-density-wave order, in which broken translation symmetry o…
The universal behaviour of the magnetic excitations in high-temperature superconductors is described in a model with static stripes retaining only the localized spin degrees of freedom. The stripes are represented by a model of coupled two-leg spin ladders. We start from the results obtained previously by continuous unitary transformations for an isolated spin ladder. A quantitative description of neutron scattering data is reached, using a model for a single cuprate layer with well established values of the exchange coupling constants. The neutron resonance peak is explained in terms of a sad…
We report the results of a ^63Cu and ^17O NMR study of the nuclear quadrupole interaction tensor, ^(17,63)nu\_{Q,alpha}, in the hole doped spin ladder system Sr\_(14-x)Ca\_xCu\_24O\_41 (x = 0 and 12) performed under ambient and high pressures. NMR data show that the hole density in the Cu\_2O\_3 ladder layer grows with temperature, Ca content and an applied pressure. We have derived the hole occupation of Cu 3d and O 2p orbitals at the different ion sites in the Cu\_2O\_3 ladder as a function of the temperature, Ca substitution and pressure. We also suggest that the most important role of high…
