Localization state induced superconductivity, pseudogap and strange metal

Abstract: The emergence of superconductivity in unconventional superconductors usually accompanies the normal-state phases of pseudogap, strange metal and Fermi liquid. It indicates these phases are strongly related to the superconducting state and should be dominated by yet unclear mechanism of superconductivity. Here, we propose a microscopic theory that, according to the coupling between localized and extended states, the pairing electrons which leap on and off a localized state result in superconducting instability. Two distinguishable pairing gaps are observed in these states, one dominates the superconducting temperature and another the temperature of a coherent pair confined at localized area. The pairing correlation between these states results in four phases. Their characteristics are manifested in universal Planckian-like resistivity and unusual carrier distribution, as observed in recent experiments.