Preformed Cooper Pairing and the Uncondensed Normal-State Component in Phase-Fluctuating Cuprate Superconductivity

Abstract: We develop a self-consistent microscopic framework beyond mean-field theory for superconductivity in cuprates. It couples fermionic quasiparticles with collective phase dynamics to treat the superconducting gap and superfluid stiffness. The phase sector explicitly incorporates both smooth bosonic Nambu-Goldstone phase fluctuations, renormalized by long-range Coulomb interactions, and topological Berezinskii-Kosterlitz-Thouless-type vortex-antivortex fluctuations. The required input is the correlated single-particle spectral function, enabling direct interfacing with Hubbard-type models. The framework provides quantitative access to key superconducting observables, including $T$-dependent gap and phase stiffness, gap-closing temperature $T_{\rm os}$, and transition temperature $T_c$, across wide ranges of doping. Using a recently proposed solvable interaction model as input, our simulations reveal several important features consistent with experimental observations in the cuprates: a $d$-wave superconducting dome in the $T$-$p$ phase diagram with a shoulder-like anomaly in the underdoped regime, a pronounced separation between $T_c$ and $T_{\rm os}$ signaling preformed Cooper pairing, a finite uncondensed normal component persisting even at $T=0$, and the onset temperature $T_{\rm on,vortex}$ of vortex signals, offering a consistent understanding of how strong correlations and phase fluctuations cooperate to shape high-$T_c$ superconductivity.