Classification of non-Fermi liquids and universal superconducting fluctuations

          @misc{ pirsa_PIRSA:25100191,
            doi = {10.48660/25100191},
            url = {https://pirsa.org/25100191},
            author = {Kukreja, Shubham},
            keywords = {},
            language = {en},
            title = {Classification of non-Fermi liquids and universal superconducting fluctuations},
            publisher = {Perimeter Institute},
            year = {2025},
            month = {oct},
            note = {PIRSA:25100191 see, \url{https://pirsa.org}}
          }
          

Abstract

Critical fluctuations coupled to Fermi surfaces can destroy conventional Fermi liquids, giving rise to diverse non-Fermi liquids that may remain metallic or become superconducting at zero temperature. I will present a classification of non-Fermi liquids with globally convex hot Fermi surfaces based on the concept of projective fixed points, which account for the flow of the Fermi momentum under renormalization. This framework organizes non-Fermi liquids into seven super-universality classes, each characterized by distinct superconducting fluctuations. Stable non-Fermi liquids exhibit universal but non-scale-invariant pairing interactions, while unstable ones display universal constraints on pairing symmetry, superconducting transition temperature, and its scaling with the Fermi momentum. I will discuss physical examples and a toy model that captures the essential universal properties of these classes.