Scale free networks of superconducting striped grains tuned at Fano resonances for high Tc

Abstract

Controlling lattice complexity or inhomogeneity of the doped oxide superconductors is shown to be a key term for control of the superconductivity critical temperature. All high temperature superconductors show anisotropic gaps and/or multi-gap superconductivity in the clean limit. They show the shape resonance in superconducting gaps that is a type of Fano resonance driven by the Josephson-like term for pairs transfer. These resonances occur where one of the multiple Fermi surface spots is near a 2.5 Lifshitz transition. The Fano antiresonance occurs between a BCS condensate and a BEC-like condensate. In a system near a 2.5 Lifshitz transition the lattice is close to an instability. This drives to the formation of a granular superconducting phase made of a charge density metal formed by puddles of ordered oxygen interstitials or ordered local lattice distortions (static short range charge density waves) detected by scanning nano-x-ray diffraction imaging. We show that the scale free networks of superconducting grains tuned to a Fano resonance is an essential feature of high temperature superconductors that favours high Tc.