Abstract
The relation between the pseudogap state and the superconducting phase in strong coupling superconductors (like cuprates and organics) is investigated by extending the self-consistent T-matrix approximation below the transition temperature (Tc). The superconducting order parameter is obtained by solving the gap equation which includes the superconducting fluctuation in a self-consistent way; the fluctuation causes the pseudogap behavior above Tc. The rapid growth of the order parameter below Tc is found to be a characteristic feature of the strong coupling superconductors. As a result of the rapid growth of the order parameter, the spectral density at the Fermi level in the one-particle spectrum rapidly decreases and that at the peak position sharply grows as soon as the system goes into the superconducting state. These observations are consistent with angle-resolved photoemission spectroscopy experiments. The properties of the one-particle spectrum above and below Tc are found to be well explained by considering the self-energy correction originating from the superconducting fluctuation and the development of the order parameter.
