Pairing Glue in the Two Dimensional Hubbard Model

TL;DR

This study uses cluster dynamical mean field calculations to analyze the superconducting gap in the 2D Hubbard model, revealing spin fluctuations as the pairing mechanism and identifying characteristic fluctuation frequencies.

Contribution

It provides a detailed frequency-dependent analysis of the pairing mechanism in the 2D Hubbard model, linking spin fluctuations to superconductivity and matching experimental data.

Findings

Pairing dominated by fluctuations at two characteristic frequencies

Lower frequency fluctuations become more significant in the pseudogap regime

The inferred pairing glue function aligns with optical conductivity data

Abstract

Cluster dynamical mean field calculations are used to construct the superconducting gap function of the two dimensional Hubbard model. The frequency dependence of the imaginary part of the gap function indicates that the pairing is dominated by fluctuations at two characteristic frequencies: one at the scale of the hopping matrix element $t$ and one at a much lower scale. The lower frequency component becomes more important as the doping is reduced into the pseudogap regime. Comparison to available information on the spin fluctuation spectrum of the model suggests that the superconductivity arises from exchange of spin fluctuations. The inferred pairing glue function is in remarkable qualitative consistency with the pairing function inferred from time-resolved optical conductivity data.