Strongly correlated superconductivity

CMP in the City 2013 4th Hubbard Theory Consortium London Summer Programme in Condensed Matter Physics
date: 
lun, 06/17/2013 to ven, 06/21/2013
Undefined
presentation: 

Non s-wave superconductivity appears in the proximity of antiferromagnetic phases in many materials, including quasi one-dimensional Bechgaard salts, layered BEDT organics, heavy fermions, iron pnictides and cuprates. There is thus strong experimental evidence for antiferromagnetically mediated superconductivity. But how do we understand this theoretically? The repulsive one-band Hubbard model naturally leads to antiferromagnetism, a phase that appears in this model from Fermi surface nesting in the weak-interaction limit and from super-exchange in the strong-interaction limit. In this talk, I will discuss similarities and differences between the normal and superconducting phases that appear in both limits. In the weak-interaction limit, the Two-Particle-Self-Consistent approach allows us to understand the origin of the pseudogap and the dome-shape of the phase diagram from antiferromagnetic fluctuations. The approach is non-perturbative and some limiting cases can be understood analytically. Dimensionality plays an important role. The phenomenology is close to that of electron-doped high-temperature superconductors. In the strong-coupling limit, we resort to Cluster Dynamical Mean-Field Theory to show that the picture of antiferromagnetically mediated superconductivity is not so simple. In the strong-interaction limit, i.e. in doped Mott insulators, the super-exchange plays a dominant role and retardation effects allow superconductivity to be surprisingly resilient to nearest-neighbor repulsion through the subtle effects of retardation. The phenomenology is similar to that of hole-doped high-temperature superconductors.