Unveiling the nature of the pseudogap and its relation to both superconductivity and antiferromagnetic Mott insulators, the pairing mechanism, and a non-Fermi liquid phase is a key issue for understanding high temperature superconductivity in cuprates. A number of experimental results gathered especially in recently years have revealed an unexpected inhomogeneous nature of cuprates at the nanoscale, indicating the fundamental inapplicability of the conventional theories based on homogeneous systems. Here we show a microscopic model of pseudogap and pairing mechanisms on the basis of the consideration of the spin state around a bound hole in a CuO2 plane and the resulting magnetic orders, leading eventually to the spin-Peierls distortion responsible for the Cooper pair formation. The present model fits and accounts for the accumulated experimental findings reported previously for cuprates, including stripe-like electronic order, breaking of the rotational symmetry, and the so-called 1/8 anomaly. We believe that the present model can help to develop a complete theoretical framework applicable to a large family of high-temperature superconductors, including ferropnictides and ferrochalcogenides.
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