We demonstrate that entanglement and confinement hole pairing (ECHP) is a precise physics of the entanglement framework of the RVB theory of high-Tc cuprates. Our novel strong ECHP mechanism explains the entire phase diagram of both electron and hole-doped cuprates, notably the linearly decreasing T* at the pseudogap but with "T*-singularity" at the peak of the superconducting (SC) dome, the Tc=T* at the optimum doping and the rest of the overdoped regions of the SC dome, the duality of the spin gap and strange metal phase, the presence of the parallel superconducting stripes in the CuO plane (spin-polarized and spin-unpolarized channels), and the linear-T resistivity of the strange metal phase above the overdoped regions of the SC dome. This also explains the experimental spin textures of the cuprates. We refer to our new ECHP model as a resonating entanglement and confinement hole pair (RECHP) theory. Based on RECHP theory, we were able to provide a conceptual and comprehensive semiquantitative explanation of the entire phase diagram, thus providing the sought-after pairing mechanism responsible for the entire phase diagram of high-T_{C} cuprates.
We demonstrate that entanglement and confinement hole pairing (ECHP) is a precise physics of the entanglement framework of the RVB theory of high-Tc cuprates. Our novel strong ECHP mechanism explains the entire phase diagram of both electron and hole-doped cuprates, notably the linearly decreasing T* at the pseudogap but with "T*-singularity" at the peak of the superconducting (SC) dome, the Tc=T* at the optimum doping and the rest of the overdoped regions of the SC dome, the duality of the spin gap and strange metal phase, the presence of the parallel superconducting stripes in the CuO plane (spin-polarized and spin-unpolarized channels), and the linear-T resistivity of the strange metal phase above the overdoped regions of the SC dome. This also explains the experimental spin textures of the cuprates. We refer to our new ECHP model as a resonating entanglement and confinement hole pair (RECHP) theory. Based on RECHP theory, we were able to provide a conceptual and comprehensive semiquantitative explanation of the entire phase diagram, thus providing the sought-after pairing mechanism responsible for the entire phase diagram of high-T_{C} cuprates.
We generalize the condition under which a quantum material exhibiting a pseudogap phase is a precursor to a superconducting (SC) dome. The result reveals the non-analytic T* as a function of doping. A well-known example is the high-Tc cuprates. Essentially, the SC dome is generated under two conditions: (1) that the pseudogap T* is a decreasing function of doping, due to the decrease in size of extended pairing of doped holes with doping, and most importantly, (2) that the rate of configurational-ordering parameter is an increasing function of doping as a result of the decrease in extended length of the disordered pairs. The theory behind these hinges on a novel strong entanglement and confinement hole pairing (ECHP) mechanism that unravels the microscopic features of the entire phase diagram of both electron and hole-doped high-Tc cuprates, recently discussed in the by Buot et al. The ECHP configurational ordering (CO) at the underdoped and overdoped regions qualitatively agrees with spin texture experiments, and strongly suggests that strange metal phase can only occur in the overdoped region, in agreement with experiments.
In high-TC cuprates, the presence of parallel superconducting stripes or rivers of charge is well established experimentally. These also act as domain walls for the antiferromagnetic order. To readily explain the pattern of superconducting stripes near and at optimal doping levels, we propose a novel strong pairing mechanism, devoid of Coulomb repulsion, for high-TC cuprates. This new mechanism is based on the quantum entanglement and connement or degree of entanglement. Some quantum entanglement experiments with antiferromagnetic-chain links directly support our proposed entanglement pairing mechanism. Depending on doping levels, the triplet and singlet pairing can either exist independently, as a "lattice" of Bell basis states with unpolarized rivers of charge for underdoped regime, or as a mixed triplet-singlet or interacting Bell basis states with spatially alternating spin-polarized superconducting stripes of charge for overdoped range. Several spin resolved (SR)-ARPES experiments on the complex spin texture of cuprates are qualitatively interpreted in the light of our novel "lattice" of coupled triplet-singlet pairing leading to polarized rivers of charge in line with experimentally-found doping-level dependence. The resulting simple intuitive model suggests that entanglement is indeed a new strong pairing mechanism, devoid of Coulomb repulsion, leading to high-TC superconductivity and strange metal behavior above TC. Moreover, our model can possibly accommodate the Meissner effect, probably as superconducting plaquettes formed by "spokes" of antiferromagnetic-chain entanglement link.
To supplement our recent brief report on the theory of holon-pair boson approach to the t-J Hamiltonian [S.-S. Lee and Sung-Ho Suck Salk, Phys. Rev. B {\bf 64}, 052501(2001)], in this paper we present a full exposure to the theory, detailed physical implications and predicted various physical properties of high Tc cuprates. We discuss the significance of coupling (interplay) between the spin and charge degrees of freedom in the Heisenberg interaction term of the t-J Hamiltonian. We discuss its importance in causing the arch-shaped superconducting transition temperature Tc and the pseudogap (spin gap) temperature T∗ tangential to Tc in the overdoped region in the observed phase diagram of high Tc cuprates. A universal parabolic scaling behavior of T∗/Tc (or Tc/T∗) with hole doping concentration is predicted in agreement with observations, indicating that there exists correlation between the pseudogap (spin gap) phase and the superconducting phase through antiferromagnetic fluctuations. Our proposed holon-pair boson theory is shown to be self-consistent in that it not only yields the arch (dome) shape structure of Tc but also reproduces various other physical properties such as superfluid weight, bose condensation energy, spectral function, optical conductivity and spin susceptibility, including their temperature and doping dependence.
Theoretical attempts to explain the origin of high temperature superconductivity are challenged by the complexity of the normal state, which exhibits three regimes with increasing hole doping: a pseudo-gap regime when underdoped, strange power laws near optimal doping and more conventional metallic behavior when heavily overdoped. We suggest that the origin of this behavior is linked to a zero temperature quantum phase transition separating the overdoped Fermi liquid from a spin-charge separated underdoped phase. Central to our analysis is a new Z2 gauge theory formulation, which supports topological vortex excitations - dubbed visons. The visons are gapped in the underdoped phase, splitting the electron's charge and Fermi statistics into two separate excitations. Superconductivity occurs when the resulting charge e boson condenses. The visons are condensed in the overdoped phase, thereby confining the charge and statistics of the electron leading to a Fermi liquid phase. Right at the quantum confinement transition the visons are in a critical state, leading to power law behavior for both charge and spin.
The phase diagram of hole-doped cuprate superconductors contains three central puzzles: a dome-shaped superconducting phase, a strange metal normal state with Planckian dissipation, and robust d-wave pairing (dx2-y2 symmetry). We propose a unified framework based on a single material-dependent parameter, the coherence purity p, which measures the fraction of phase-coherent condensate relative to dissipative channels. Geometric frustration of the antiferromagnetic background on the CuO2 square lattice drives p to a maximum at optimal doping. The superconducting transition temperature follows T_c proportional to p/(1-p). The d-wave symmetry is derived as the leading pairing instability under on-site repulsion and nearest-neighbor superexchange, without being assumed. In the strange metal, the Planckian dissipation coefficient alpha = hbar/(tau kB T) is linked to the purity deficit 1-p through a universal amplification factor C ≈ 31, which we derive from the nodal Dirac structure of the d-wave state. Fitting the superconducting domes of LSCO and YBCO with the peak purity p_max = 0.97 (fixed from independent transport and high-energy experiments) yields excellent agreement using only two material-dependent scale parameters. The framework produces falsifiable predictions for the doping dependence of the superfluid density and for the product of maximum T_c and the Planckian coefficient. Keywords: high-temperature superconductivity, cuprates, strange metal, Planckian dissipation, d-wave pairing, coherence purity, superconducting dome, LSCO, YBCO
There are two seemingly unrelated puzzles about the cuprate superconductors. The first puzzle concerns the strong non-BCS behavior around xc, the end point of the superconducting dome on the overdoped side, where the cuprate is believed to be well described by the Fermi-liquid theory. This is the most evident in the observed ${\ensuremath{\rho}}_{s}(0)\ensuremath{-}{T}_{c}$ scaling and the large amount of uncondensed optical spectral weight at low energy. The second puzzle concerns the remarkable robustness of the d-wave pairing against the inevitable disorder effect in such a doped system, which is also totally unexpected from the conventional BCS picture. Here we show that these two puzzles are deeply connected to the origin of a third puzzle about the cuprate superconductors, namely, the mysterious quantum critical behavior observed around x∗, the so called pseudogap end point. Through a systematic variational Monte Carlo (VMC) study of the disordered 2D $t\ensuremath{-}J$ model from the resonating valence bond (RVB) perspective, we find that the d-wave pairing in this model is remarkably more robust against the disorder effect than that in a conventional d-wave BCS superconductor. We find that such remarkable robustness can be attributed to the spin-charge separation mechanism in the RVB picture, through which the d-wave RVB pairing of the charge-neutral spinons becomes essentially immune to the disorder potential except for the secondary effect related to the modulation of the local doping level by the disorder. We propose that there exists a Mott transition at x∗, where the RVB pairing in the underdoped regime is transmuted into the increasingly more BCS-like pairing for x>x∗, whose increasing fragility against the disorder effect leads to the non-BCS behavior and the ultimate suppression of superconductivity around xc.