Superconductivity in the Attractive Hubbard Model: The Double Hubbard--I Approximation

J. J. Rodríguez--Núñez, H. Ghosh

Using the Dyson equation of motion for both the diagonal one-particle Green function, $G(\vec{k},\omega )$ and off--diagonal Green function, $F(\vec{k},\omega )$, at the level of the Hubbard--…