Fluctuating Pair-Density Wave in anisotropic strongly coupled pairing system

In weakly coupled BCS superconductors, only electrons within a tiny energy window around the Fermi energy form Cooper pairs. This may not be the case in strong coupling superconductors such as FeSe, SrTiO3 or cold atom condensates where the pairing scale becomes comparable or even larger than the Fermi energy. In this talk I will discuss an analytically solvable model to examine possible pairing phases in the strongly coupled regime in the presence of anisotropic interactions. I will illustrate the properties of a novel finite temperature phase where local pair correlations have non-zero center-of-mass momentum but lack long-range order. Below a critical temperature such a fluctuating pair-density wave phase can condense either to a uniform d-wave superconductor or to a pair-density wave phase depending on the strength of the pairing interaction. I will conclude discussing possible realizations of our mechanism, including cuprates, where the pseudogap phase has been postulated to be a form of incoherent pair density wave.