High-temperature superconductivity in cuprates and organics : where do we stand ? (6)

Some of the first ideas on d-type superconductivity mediated by antiferromagnetic fluctuations arose from a collaboration between Orsay and Sherbrooke in the 80s. In this lesson, I explain the two-particle self-consistent approach to the Hubbard model, developed in the 90s. This approach is non-perturbative but controlled by sum rules and consistency criteria. I first demonstrate how the approach works and present comparisons with standard calculations in the normal state. I discuss how some experiments in the normal state of electron-doped cuprates, including the pseudogap, can be explained by this approach. I conclude with superconductivity mediated by antiferromagnetic fluctuations, explaining the optimal conditions for pairing. In the second part, I move on to a more formal approach and discuss some open questions.