Mean-field approach to unconventional superconductivity

Abstract

We propose a model that connects the quasiparticle spectral function of high-Tc superconductors to the condensation energy. Given the evidence for pair correlations above Tc, we consider a coarse-grain Hamiltonian of fluctuating pairs describing the incoherent pseudogap (PG) state, together with a novel pair–pair interaction term that restores long-range superconducting (SC) coherence below Tc. A mean-field solution then leads to a self-consistent gap equation containing the new pair–pair coupling. The corresponding spectral function A(k,E) reveals the characteristic peak–dip–hump features of cuprates, now observed on iron pnictides (LiFeAs). The continuous transition from SC to PG states is discussed.