Talk 1:
Analogies between classical and electronic fluids: Widom and Frenkel lines with applications to the Hubbard model
André-Marie Tremblay, University of Sherbrooke
Many concepts of statistical physics have surprisingly wide applicability, from simple flu-ids to QCD. In this talk, I will discuss crossovers that appear above first-order transitions that end at a critical endpoint. In classical fluids, the first-order transition I consider is the liquid-gas transition and the crossovers are defined by the Widom line for thermody-namic quantities and by the Frenkel line for dynamical ones. I will present results for the electronic fluid obtained from cluster extensions of dynamical mean-field theory for the Hubbard model. The first-order transitions are the Mott transition at half-filling and the Sordi transition at finite doping. I will discuss the relevance of these concepts to cupra-tes and layered organics.
Talk 2:
Correlation Enhanced Electron-Phonon Coupling in FeSe/SrTiO3 at a Magic Anglen
Subhasish Mandal, West Virginia University
Electron–phonon coupling (EPC) is a fundamental quantity in many-body physics, governing diverse material properties and phenomena. Its intricate interplay with strongly correlated electrons remains a central topic of investigation in Fe-based superconductors, where a predictive theory for unconventional superconductiv-ity is still lacking. Building on this understanding, controlling the superconducting transition temperature (Tc) through atomic-scale structural engineering and its connection to strong electronic correlations offers a promising pathway toward high-Tc materials. Here, by combining first-principles embedded dynamical mean-field theory calculations with epitaxial growth of single-layer FeX (X = Se, S, Te) on a SrTiO3 (001) substrate, which enables controlled distortion of the FeX4 tetrahedron, we uncover a distinct superconducting dome where the superconducting gap reach-es its maximum at a ‘magic’ angle of the FeX4 tetrahedron and the EPC for the A1g phonon mode is maximized for the FeSe film. Our findings reveal a significant role of electronic correlations in strengthening Cooper pairing in unconventional supercon-ductors by enhancing EPC.
