Magnetic-texture-driven charge pairing in the spin-fermion Hubbard model and superconductivity in the high-Tc cuprates

Abstract

We propose a model for high-Tc superconductors that considers the spin fluctuations of the localized moments of copper and the fluctuations of the doped holes in oxygen as independent degrees of freedom. We argue that the Coulomb interaction between the doped holes becomes important as the doping concentration increases and produces changes in the basic properties of the system. The holes are fractionalized with their charge being associated with magnetic texture (Skyrmion) excitations of the Copper spin background whereas their spin is carried by chargeless fermion excitations. Charge pairing is driven by the interaction between the magnetic textures, which in the quantum-disordered phase that precedes the superconducting transition are fully quantum mechanical and gapless. The quantum Skyrmion effective interaction potential is evaluated as a function of doping and temperature, indicating that Cooper pair formation is determined by the competition between these two types of spin fluctuations (copper and oxygen). The superconducting transition occurs when the effective potential allows for Skyrmion bound states and this is expressed as an algebraic equation relating Tc to other microscopic parameters and doping. Our theoretical predictions for the superconducting phase diagram of La2−xSrxCuO4 and YBa2Cu3O6+x are in good agreement with experiment in the underdoped region.

Source-reported materials — not catalogue approval

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