An explanation for the pseudogap of high-temperature superconductors   based on quantum optics
  We first explain the pseudogap of high-temperature superconductivity based on an approach of quantum optics. After introducing a damping factor for the lifetime $\tau$ of quasiparticles, the superconducting dome is naturally produced, and the pseudogap is the consequence of pairing with damped coherence. We derive a new expression of Ginzburg-Landau free energy density, in which a six-order term due to decoherence damping effect is included. Without invoking any microscopic pairing mechanism, this approach provides a simple universal equation of second-order phase transition, which can be reduced to two well-known empirical scaling equations: the superconducting dome Presland-Tallon equation, and the normal-state pseudogap crossover temperature $T^{*}$ line. 
Deshui Yu, Jingbiao Chen