On Fermi surfaces
Dominic Else
Perimeter Institute
Wednesday, October 4, 2023
10:30 a.m.
In-person: QNC 1101
Abstract: Metals are a very general concept that can apply beyond conventional theories such as Fermi liquid theory. In this talk, I address the question: what are the most general properties of metals, and how should we define them? In particular, I argue that the most fundamental property of a metal is the existence of a "Fermi surface" in momentum space. I moreover argue that the most general definition of Fermi surface, applicable even in strongly interacting systems, is via the associated emergent symmetry, and the anomaly of that emergent symmetry. I discuss several applications of these ideas: firstly, I use them to develop improved "holographic" models of non-Fermi liquid metals that explicitly incorporate the Fermi surface; secondly, I show that applying hydrodynamics to the conservation laws resulting from the emergent symmetry associated with the Fermi surface strongly constrains the dynamical modes of the system, essentially recovering the same equations of motion as in Fermi liquid theory without needing to assume anything about the existence of quasiparticles.