DMFT-QE Symposium: April 15

Talk 1:

Insight into Hund metals and interplay with Mott physics

Luca de’ Medici, ESPCI Paris

Hund metals are paramagnetic phases in which high-spin local configurations dominate. This paradigm is now a useful guidance to interpret the physics of many transition-metal compounds, like Ruthenates and Iron-based superconductors. I will show how this physics is extremized by moving towards a half-filled Mott insulator, and that it gives rise to charge instabilities and heavy fermionic behavior along the way.

A. Georges and G. Kotliar, Physics Today 77, 46 (2024)
M. Chatzieleftheriou et al. Phys. Rev. Lett. 130, 066401 (2023)
M. Crispino et al. ArXiv:2312.06511 (2023)

Talk 2:

Hund’s driven correlation, nematicity and superconductivity in iron-based superconductors

Laura Fanfarillo, Institute of Complex System ISC-CNR

Iron-based superconductors represent an intriguing playground to study the role of electronic correlation in the realization of quantum orders. On the one hand a wealth of evidence shows that the phenomenology of the normal state can be fully accounted in terms of Hund’s metal physics, on the other hand the emergence of quantum orders at low-temperature can be explained as the results of Fermi surface instabilities and studied within conventional theories based on the exchange of low-energy bosons.

By studying how nematicity and superconductivity are affected by the presence of Hund’s driven correlations, we are able to reconcile these two perspectives and unveil the non trivial role of correlations on the realization of those quantum states.  The key novelty of the study is the inclusion of the dynamical features of correlations 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 distinguish the specific nematic spectral features characterizing the Hund’s metal with respect to a standard correlated metal [1] and to unveil the crucial role of the redistribution of spectral weight of the Hund’s metal to promote superconductivity [2].

Our analysis provides a new building block towards the full comprehension of quantum orders in correlated systems and proves that the dynamical renormalization effects, often neglected in the analysis of the experimental data, strongly affect both qualitatively and quantitatively the realization of quantum orders in those systems.

[1]. L. Fanfarillo, A.Valli, M.Capone, Physical Review B 107, L081114 (2023)

[2]. L. Fanfarillo, A.Valli, M.Capone, Phys. Rev. Lett. 125, 177001 (2020)