How Much Phase Coherence Does a Pseudogap Need?

Abstract

It has been suggested that the ``pseudogap'' regime in cuprate superconductors, extending up to hudreds of degrees into the normal phase, reflects an incoherent d-wave pairing, with local superconducting order coherent over a finite length scale $ξ$, insufficient to establish superconductivity. We calculate the single-particle spectral density in such a state from a minimal phenomenological disordered BCS model. When the phase-coherence length exceeds the Cooper pair size, a clear pseudogap appears. The pseudogap regime, however, is found only over a relatively narrow range of phase stiffnesses, hence is not expected to extend more than about 20% above $T_c$.