Mechanism of Superconductivity in the Hubbard Model at Intermediate Interaction Strength

TL;DR

This paper investigates the pairing mechanism in the 2D Hubbard model at intermediate interaction strength, identifying antiferromagnetic fluctuations as the key driver of d-wave superconductivity, with implications for understanding unconventional superconductors.

Contribution

It provides a detailed analysis of the fluctuation mechanisms leading to superconductivity in the Hubbard model using cluster dynamical mean-field theory, highlighting differences from conventional theories.

Findings

Antiferromagnetic fluctuations are identified as the pairing glue.

The dominant magnetic fluctuations differ from conventional spin-fluctuation theory.

Superconductivity persists in both underdoped and overdoped regimes.

Abstract

We study the fluctuations responsible for pairing in the $d$-wave superconducting state of the two-dimensional Hubbard model at intermediate coupling within a cluster dynamical mean-field theory with a numerically exact quantum impurity solver. By analyzing how momentum and frequency dependent fluctuations generate the $d-$wave superconducting state in different representations, we identify antiferromagnetic fluctuations as the pairing glue of superconductivity both in the underdoped and the overdoped regime. Nevertheless, in the intermediate coupling regime, the predominant magnetic fluctuations may differ significantly from those described by conventional spin-fluctuation theory.