Mechanism of superconductivity in the Hubbard model at intermediate interaction strength*

The mechanism of electronic superconductivity in systems with intertwined orders has long been debated.

Several electronic mechanisms have been proposed, but so far there is no unbiased way of attributing superconductivity to any one of them. Here we analyze the nature of superconductivity in a non-perturbative calculation of the two-dimensional Hubbard model within the dynamical cluster approximation, which treats all possible fluctuations on equal footing. 

We show that the anomalous self energy at intermediate-to-strong interaction strengths results primarily but not exclusively from spin fluctuations. Our results resolve the long-standing question of the pairing glue in this model.