Plaquette valence bond theory of high-temperature superconductivity

Malte Harland; Mikhail I. Katsnelson; Alexander I. Lichtenstein

doi:10.1103/PhysRevB.94.125133

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Plaquette valence bond theory of high-temperature superconductivity

Malte Harland, Mikhail I. Katsnelson, Alexander I. Lichtenstein

DOI 10.1103/PhysRevB.94.125133 · Physical Review B

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Abstract

We present a strong-coupling approach to the theory of high-temperature superconductivity based on the observation of a quantum critical point in the plaquette within the t,t′ Hubbard model. The crossing of ground-state energies in the N=2–4 sectors occurs for parameters close to the optimal doping. The theory predicts the maximum of the dx2−y2-wave order parameter at the border between localized and itinerant electron behaviors and gives a natural explanation for the pseudogap formation via the soft-fermion mode related to local singlet states of the plaquette in the environment. Our approach follows the general line of resonating valence-bond theory stressing a crucial role of singlets in the physics of high-Tc superconductors but focuses on the formation of local singlets, similar to phenomena observed in frustrated one-dimensional quantum spin models.