Pairing boost from enhanced spin-fermion coupling in the pseudogap regime

TL;DR

This paper analyzes how spin fluctuations influence pairing interactions in the Hubbard model, revealing a strong coupling in the pseudogap regime that sustains superconductivity despite incoherent quasiparticles.

Contribution

It demonstrates that spin-fermion coupling mediates a significant attraction in the pseudogap regime, providing insight into superconductivity in underdoped cuprates.

Findings

Spin fluctuations open a pseudogap in the underdoped regime.

Giant attraction between antinodal fermions mediated by spin-fermion coupling.

Superconductivity persists despite lack of coherent quasiparticles.

Abstract

We perform a fluctuation analysis of the pairing interaction in the hole-doped Hubbard model within the dynamical cluster approximation. Our analysis reveals that spin-fluctuation-mediated pairing differs qualitatively in the over- and underdoped regimes. In the underdoped regime, spin fluctuations open a pseudogap. We show that in this regime the spin-fermion coupling mediates a giant attraction between antinodal fermions. This explains why superconductivity survives at underdoping in the Hubbard model and cuprates, despite the lack of coherent fermionic quasiparticles in the pseudogap regime.