Mean-field approach to unconventional superconductivity

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.