Unconventional superconductivity and Hund’s induced electron correlations: a cooperative mechanism

Thirty years of research has established the emergence of a new paradigm in which strong electron-electron correlations and superconductivity are strongly intertwined. A number of successful approaches have improved our understanding of this link in high-temperature copper-based superconductors and in other families, including the iron-based materials. However, a general framework to understand how superconductivity emerges in systems dominated by electron-electron repulsion is still lacking.

In this talk I will focus on the analysis of this problem in the context of iron-based superconductors. First I will provide a brief overview of the experimental evidences of the strong orbital-dependent electronic correlations characterizing the paramagnetic phase of iron-based superconductors and I will discuss this phenomenology in terms of Hund’s metal physics. Then, I will present our results on the role of those electronic correlations on the superconductivity driven by a generic weak-coupling mechanism (e.g. the coupling to a boson). The key novelty of the study is the inclusion of the dynamical properties that make a Hund’s metal substantially different with respect to both a weakly interacting metal and to an ordinary correlated metal with a large effective mass renormalization. This allows us to unveil the crucial role of the redistribution of spectral weight of the Hund’s metal to promote superconductivity and to enhance the orbital-selective character of the gap functions.

Host: Peter Hirschfeld