The theory of the high temperature superconducting cuprates, which is based on the condensation of holes into strings in checker-board geometry, was successful to explain the elastically scattered Neutrons by spin waves. Here it is extended to analyze the inward dispersion curve of its inelastic counterpart, up to the resonance energy- . This extension is done by applying the perturbation theory of the linear response to the condensed strings. The approximated susceptibility is derived by means of the ring diagram. The dispersion relation is obtained from the dispersion of the poles of the susceptibility integral. It is found that the particle anti-particle pair that yields the susceptibility is the time reversal pair where the particle momentum is in phase A, and the anti-particle momentum is in phase B. The dispersion is found to be in agreement with experiment, subject to some suggested corrections. The weak intensity by the resonance energy, as well as the dispersion, is speculated to be modified due to interference with spin waves that are caused by direct spin flip, as in the mother undoped materials.
Here we suggest a simple physical model of HTSC cuprates that provides qualitative explanation of the main features of these compounds, including the nature of Fermi arcs, pseudogap anomalies and the origin of free carriers. According to this model, the unusual properties of HTSC cuprates result from their unique electronic structure favourable for the formation of diatomic negative-U centers (NUCs) and realization of an unusual mechanism of electron-electron interaction.
This work is based on the double correlated linear aggregations of holes in checkerboard geometry. It is proved that the pairing function symmetry is - d(x*x-y*y), as been observed experimentally. It is also shown that there is a "superconductive spin gap" for the observation of the magnetic incommensurate modulation peaks, in agreement with experiment. In addition, the unperturbed Hamiltonian is reanalyzed and modified.
The direct exchange integral and the transfer integral are calculated for the anti-bonding wave-function of the HTSC cuprates. The direct exchange integral yields a value three times larger than the indirect exchange of the t-J Hamiltonian. It also predicts positive exchange energy for neighboring parallel spins, contrary to the prediction of zero energy by the t-J Hamiltonian. A modified t-J Hamiltonian is proposed, and the implications of the results are discussed.
This paper reviews experimental phase diagrams of cuprates and pnictides to demonstrate that specific features of the superconducting phase diagrams in bothHTSC families can be understood within the framework of the proposed approach,which assumes the formation, under heterovalent doping, of localized trion complexes consisting of a doped carrier and charge transfer (CT) excitons. The geometry of such cells containing CT excitons (CT plaquettes) in the basal plane of the crystal is determined by its crystal structure and the type of dopant, so that the dopant concentration range corresponding …
Spin dynamics in HTSC cuprates: The singlet--correlated band (or t-J-V) model and its applications
迄今为止，铜氧化物超导态自旋磁化率的计算都是在弱耦合近似下进行的。然而，已知铜酸盐属于Mott-Hubbard掺杂材料，其中电子相关性是重要的。本文在考虑强关联的单重关联能带模型下，导出了铜氧化物超导态自旋磁化率的解析表达式。自旋磁化率的表达式进行评估，使用的跳跃参数的值适合于测量的费米面的材料YBa 2Cu 3 O 7和Bi 2Sr 2CaCu 2 O 8。我们表明，现有的实验数据，这是直接相关的自旋磁化率可以解释一致的一组模型参数为每种材料。这些实验包括由非弹性中子散射观察到的磁共振峰和超导状态下NMR自旋位移、自旋-自旋和自旋-晶格弛豫速率的温度依赖性。
New electronic Raman and I.R. spectroscopy results from optimally and overdoped high temperature superconducting (HTSC) cuprate systems are interpreted in terms of the negative-U, boson-fermion crossover model. Distinction is made between those features which follow the condensate gap, 2Delta(p), and those that are set by the local-pair binding energy, cursive U(p). The critical role of doping level psubc = 0.185 is highlighted in conjunction with the matter of developing quasiparticle incoherence, making connection here with recent transport and related results. E//c IR results in magnetic fi…
Earlier we have proposed a new approach to the analysis of superconducting phase diagrams for cuprates and pnictides and have shown that the positions of superconducting domes on the diagrams can be predicted with high accuracy proceeding from only the crystal structure of a particular compound. The proposed approach uses the concept of the self-localization of doped carriers due to their formation of trion complexes that represent a bound state of the doped carrier and charge transfer excitons emerging under its influence. Here, as exemplified by cuprates, we show that the use of the proposed…
We propose a generalized model of electronic structure modification in HTSC cuprates and ferropnictides under doping. In this model the role of doping consists in only a local change in the electronic structures of the parent phases of cuprates and ferropnictides due to the formation of trion complexes comprising a doped carrier localized in unit cell and charge transfer (CT) excitons around it. These CT excitons emerge in CuO4 or AsFe4 plaquettes in the CuO2 or FeAs basal planes (CT plaquettes) under the influence of doped carrier, restricting its itinerancy. As the dopant concentration is in…
Examination of the claim by Loram and Tallon that the energy-resolved STM results, in their apparent inhomogeneity, misrepresent the true bulk behaviour of the HTSC cuprates
In Part I we discuss accumulating experimental evidence related to the structure and origin of the bosonic spectral function in high-temperature superconducting (HTSC) cuprates at and near optimal doping. Some global properties of the spectral function, such as number and positions of peaks, are extracted by combining optics, neutron scattering, ARPES and tunnelling measurements. These methods give convincing evidence for strong electron-phonon interaction (EPI) with the coupling constant between 1-3 in cuprates near optimal doping. Here we clarify how these results are in favor of the Eliashb…
The possibility of inducing topological superconductivity with cuprate high-temperature superconductors (HTSC) is studied for various heterostructures. We first consider a ballistic planar junction between a HTSC and a metallic ferromagnet. We assume that inversion symmetry breaking at the tunnel barrier gives rise to Rashba spin-orbit coupling in the barrier and allows equal-spin triplet superconductivity to exist in the ferromagnet. Bogoliubov-de Gennes equations are obtained by explicitly modeling the barrier, and taking account of the transport anisotropy in the HTSC. By making use of the …
In this work, the concentration and temperature dependences of the superconducting gap of the HTSC cuprate in the orthorhombic phase are obtained within the framework of the Hubbard model taking into account the exchange mechanism of pairing. The enhanced s*-wave component of the superconducting gap against the background of the prevailing d-wave component in a narrow range of hole concentrations in the overdoped region is found. To elucidate the reasons for such unusual behavior the electronic structure of the low-energy excitations and the structure of the contributions of the pair states to…
HTSC Cuprate Phase Diagram Using a Modified Boson-Fermion-Gossamer Model Describing Competing Orders, a Quantum Critical Point and Possible Resonance Complex
Electron-phonon coupling (EPC) is one of the most common and fundamental interactions in solids. It not only dominates many basic dynamic processes like resistivity, thermal conductivity etc, but also provides the pairing glue in conventional superconductors. But in high-temperature superconductors (HTSC), it is still controversial whether or not EPC is in favor of paring. Despite the controversies, many experiments have provided clear evidence for EPC in HTSC. In this paper, we briefly review EPC in cuprate and iron-based superconducting systems revealed by Raman scattering. We introduce how …
A negative-U interpretation of the femto-second laser pulse induced crystallographic expansion of a cuprate HTSC material reported recently by Gedik et al
We have performed a temperature dependent angle-resolved photoemission spectroscopy (ARPES) study of the tri-layer high-$T_c$ cuprate superconductor (HTSC) Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+δ}$ (Bi2223), and have shown that the \textquotedblleft effective\textquotedblright superconducting (SC) gap $Δ_{\rm{sc}}$ defined at the end point of the Fermi arc and the $T_c$ (= 110 K) approximately satisfies the weak-coupling BCS-relationship 2$Δ_{\rm{sc}}$ = 4.3$k_{\rm{B}}T_c$. Combining this result with previous ARPES results on single- and double-layer cuprates, we show that the relationship between 2$…
Two-particle (2-p) excitations such as spin and charge excitations play a key role in high-Tc cuprate superconductors (HTSC). On the basis of a parameter-free theory, which extends the Variational Cluster Approach (a recently developed embedded cluster method) to 2-p excitations, the magnetic excitations of HTSC are shown to be reproduced for a Hubbard model within the relevant strong-coupling regime. In particular, the resonance mode in the underdoped regime, its intensity and "hour-glass" dispersion are in good overall agreement with experiments.
Novel results in STM, ARPES, HREELS, Nernst, neutron, Raman, and isotope substitution experiments and their relation to bosonic modes and charge inhomogeneity, from perspective of negative-Ueff boson-fermion modelling of HTSC
Topological Theory of Electron-Phonon Interactions in High Temperature Superconductors
在最佳掺杂的铜氧化物高温超导体（HTSC）的光电子能谱（ARPES）中观察到的声子扭结中存在较大的同位素效应，但它们与具有强电子-声子相互作用的近自由电子金属的预期声子扭结有很大不同（Gweon et al. 2004）。这些差异，以及红外光谱中的许多其他异常，似乎表明其他粒子（如磁振子）必须有助于高温超导。在这里，我们使用拓扑（非哈密顿）的方法来讨论的数据，强调纳米级的相分离和附近的费米能量，空间上钉扎到一个自组织的非线性掺杂剂阵列的量子双稳态的窄带的重要性。拓扑离散，非连续，非微扰的方法以前解释了HTSC相图的形式，而不涉及详细的微观假设，他们是特别有用的存在下，强烈的纳米级的障碍。这些方法也解释了“奇迹”的一个理想的近自由电子声子扭结在明确定义的节点准粒子状态在LSCO在金属-绝缘体过渡。最后，在不同的铜酸盐的扭结能量和费米速度的普遍性是这些材料的边缘弹性性质的结果，特别是均衡的CuO 2平面的字符。
High-temperature superconductivity (HTSC) mysteriously emerges upon doping holes or electrons into insulating copper oxides with antiferromagnetic (AFM) order. It has been thought that the large energy scale of magnetic excitations, compared to phonon energies for example, lies at the heart of an electronically-driven superconducting phase at high temperatures. However, despite extensive studies, little information is available for comparison of high-energy magnetic excitations of hole- and electron-doped superconductors to assess a possible correlation with the respective superconducting tran…
以前，我们在铜酸盐和相关材料的应用中，通过WZWN模型指出了量子群[Phys. Lett A272，（2000）]与弦之间的关系，量子群与弦之间的联系是证明我们先前猜想有效性的一种方式[即铜酸盐理论可以在量子群的基础上构建]。铜氧化物似乎表现出统计，维数和相变在新的方式。必须理解激发的性质[即准粒子或集体激发]。哈伯德模型捕捉到了这些材料中的相变的一些行为。另一方面，这些材料中的条纹等相与量子群或类弦解有关。因此，人们期望哈伯德模型的相关解可以用弦解来表示。简而言之，这种方法可能导致哈伯德和其他凝聚态哈密顿量的非微扰公式。问题是，如何一个1-d为基础的对称性，如量子群可以在描述一个3-d [空间维度]系统，如铜氧化物相关。答案在于关键的观察，即弦是一维物体，可以用来描述$d$维的物理。例如，引力[是一种三维空间加时间的]现象可以用一维弦来理解。因此，我们预期一维量子群物体会引发二维和三维的物理现象，这可能与铜氧化物有关。我们提出支持我们的论点，使用[数值]变分蒙特卡罗[MC]适用于二维d-p模型。我们还简要地讨论了其他的方法来制定一个字符串图片的铜氧化物，即利用之间的联系规范理论和字符串和t 'Hooft图片的夸克禁闭。
A term first coined by Mott back in 1968 a `pseudogap' is the depletion of the electronic density of states at the Fermi level, and pseudogaps have been observed in many systems. However, since the discovery of the high temperature superconductors (HTSC) in 1986, the central role attributed to the pseudogap in these systems has meant that by many researchers now associate the term pseudogap exclusively with the HTSC phenomenon. Recently, the problem has got a lot of new attention with the rediscovery of two distinct energy scales (`two-gap scenario') and charge density waves patterns in the cu…
Many puzzling properties of high-$T_c$ superconducting (HTSC) copper oxides have deep roots in the nature of the antinodal quasiparticles, the elementary excitations with wavevector parallel to the Cu-O bonds. These electronic states are most affected by the onset of antiferromagnetic correlations and charge instabilities and they host the maximum of the anisotropic superconducting gap and pseudogap. In this work, we use time-resolved extreme-ultra-violet (EUV) photoemission with proper photon energy (18 eV) and time-resolution (50 fs) to disclose the ultrafast dynamics of the antinodal states…
In strongly-correlated systems the electronic properties at the Fermi energy (EF) are intertwined with those at high energy scales. One of the pivotal challenges in the field of high-temperature superconductivity (HTSC) is to understand whether and how the high energy scale physics associated with Mott-like excitations (|E-E$_{F}$|>1 eV) is involved in the condensate formation. Here we show the interplay between the many-body high-energy CuO2 excitations at 1.5 and 2 eV and the onset of HTSC. This is revealed by a novel optical pump supercontinuum-probe technique, which provides access to the …
25 years after discovery of high-temperature superconductivity (HTSC) in La$_{2-x}$Ba$_x$CuO$_4$ (LBCO), the HTSC continues to pose some of the biggest challenges in materials science. Cuprates are fundamentally different from conventional superconductors in that the metallic conductivity and superconductivity are induced by doping carriers into an antiferromagnetically ordered correlated insulator. In such systems, the normal state is expected to be quite different from a Landau-Fermi liquid - the basis for the conventional BCS theory of superconductivity. The situation is additionally compli…
When investigating low-frequency (0.1 Hz) oscillations of miltiphase high-temperature cuprate superconductors (HTSC) Bi1,7Pb0,3Sr2Ca(n-1)CunOy (n=2-30), a wide attenuation peak with a maximal at T=200K detected. This peak was particularly pronounced in field cooling (FC) experiments, i.e. after abrupt cooling of the sample in the external magnetic field at the temperature T less Tc with subsequent slow warming up to room temperature with invariance of applied field. The attenuation peak height depended on the preliminary orientation (before cooling) of the samples in the measured permanent mag…
The effect of the Coulomb repulsion of holes on the Cooper instability in an ensemble of spin-polaron quasiparticles has been analyzed, taking into account the peculiarities of the crystallographic structure of the CuO$_2$ plane, which are associated with the presence of two oxygen ions and one copper ion in the unit cell, as well as the strong spin-fermion coupling. The investigation of the possibility of implementation superconducting phases with d-wave and s-wave pairing of the order parameter symmetry has shown that in the entire doping region only the d-wave pairing satisfies the self-con…
Oxygen Nuclear Magnetic Resonance Study of RuSr2EuCu2O8
我们报告的结果从17 O核磁共振（NMR）研究的高温超导铜酸盐（HTSC），RuSr 2 EuCu 2 O 8。最近发现这种化合物表现出磁有序和超导性共存。在9 T时，RuO 2层中的磁序主要是铁磁性的。我们测量了17 O NMR谱从10 K到330 K，发现发生的增加17 O NMR位移随着温度的升高，温度高于200 K，提供直接证据表明，RuSr 2 RCu 2 O 8是类似于一个非常欠掺杂的HTSC。17 O NMR线的NMR位移和光谱宽度的分析给出了一个小的，但可测量的超精细场~9 mT的Ru时刻在铜氧平面中的氧位点。我们发现，17 O NMR线宽是由偶极贡献Ru时刻。
The quantum oscillation data from a whole variety of underdoped HTSC systems and physical measurements has almost universally been presented in very classical terms following the Lifshitz-Kosevich formulation for Fermi-Landau quasiparticles, quantized into vortices and Landau levels under the high applied magnetic fields. The Fermi surface always emerges as a very small fraction of the large parent Fermi surface detected at higher doping. This then calls for some Fermi surface reconstruction to have occurred, as from a charged density wave, etc.. The paper refutes this reciprocal space approac…
Zigzag Filamentary Theory of Broken Symmetry of Neutron and Infrared Vibronic Spectra of YBa2Cu3O(6+x)
丝状高温超导理论（英语：Filamentary high temperature superconductance，HTSC）与连续高温超导理论有着根本的不同，因为它强调的是自组织的、离散的掺杂网络，并且没有进行有效介质近似（英语：Effective medium approximation，EMA）。分析中子和红外（特别是与c轴偏振）振动光谱，主要是YBa_2Cu_3O（6+x），在超导框架内，表明所观察到的振动异常附近400 cm-1（50 meV）与曲线超导路径。这些路径穿过铜酸盐链和平面以及BaO层中的共振隧穿中心。分析和数据证实了早期的cu 〇 2平面中包含3-4 nm的铁弹域的纳米结构模型;正是这些纳米结构域负责电子和电子振动性质的离散玻璃性质。中子和光子散射的电子振动能量和振子强度的化学趋势在连续模型中是异常的，很容易由非连续模型解释。
Arguably the most intriguing aspect of the physics of cuprates is the close proximity between the record high-Tc superconductivity (HTSC) and the antiferromagnetic charge-transfer insulating state driven by Mott-like electron correlations. These are responsible for the intimate connection between high and low-energy scale physics, and their key role in the mechanism of HTSC was conjectured very early on. More recently, the detection of quantum oscillations in high-magnetic field experiments on YBa2Cu3O6+x (YBCO) has suggested the existence of a Fermi surface of well-defined quasiparticles in u…
