Alessandro Toschi

Affiliation: Institute of Solid State Physics (Technische Universität Wien)
Research Interests: Theoretical Physics, Electronic Correlations, Superconductivity, Quantum Criticality
Title: Local Moment Formation and Kondo screening from the Charge-Sector Perspective: How Perturbation Theory breaks down
Abstract: In this talk, I will discuss how the correct physical description of the formation of local moments and of their Kondo screening gets reflected in the charge-scattering sector. In particular, by a systematic analysis of the on-site charge and spin fluctuations on Hubbard atom, Anderson Impurity Model and Hubbard model solved by means of dynamical mean-field theory, I will demonstrate [1] how the strong intertwining between the different (spin and charge) sectors, which is crucial for a coherent description of correlated metallic and Mott insulating phases, necessarily drives the breakdown of the self-consistent perturbation expansion [1,2].
The improved understanding of the frequency structures of the two-particle correlation functions has also allowed us [2] to identify the typical fingerprints of the Kondo physics in the charge sector and, on an even more quantitative level, to introduce a new, quite accurate criterion for estimating the Kondo temperature. Interestingly, the same scattering processes responsible for the on-site charge localization may result in an effective electronic attraction [3,4], triggering the phase-separation instabilities emerging in the proximity of Mott-Hubbard or Hund’s-Mott metal-insulator transitions.