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 where the pairing scale, becomes comparable or even larger than the Fermi one.
During my time at UF I collaborated with Chandan Setty and Peter Hirshfeld on this topic and our work got finally published on Nature Communications!
We study an analytically solvable model to examine pairing in the strongly coupled regime and in the presence of anisotropic interactions. Already for moderate coupling we find an unusual finite temperature phase, below an instability temperature, where local pair correlations have non-zero center-of-mass momentum but lack long-range order. At low temperature, this fluctuating pair density wave can condense either to a uniform d-wave superconductor or the widely postulated pair-density wave phase depending on the interaction strength. Our minimal model offers a unified framework to understand the emergence of both fluctuating and long range pair density waves in realistic systems.
Laura Fanfarillo 