Dr. Dominic Else - Perimeter Institute


Title: Universal properties of metals



Electrons insolid-state materials often form metallic ground states, in which (in thehypothetical limit of a totally clean system) the conductivity increasestowards infinity as the temperature goes to zero. Conventional metals arewell-described by Fermi liquid theory, in which the low-energy excitations arequasiparticles, i.e. dressed versions of the microscopic electrons, sitting ona "Fermi surface" in momentum space. However, Fermi liquid theoryfails to describe the physics seen in many materials, such as the high-Tccuprates. Such "non-Fermi liquid" metals presumably constitute astrongly interacting "quantum soup" in which the identity of theindividual quasiparticles has been lost. Despite many valiant efforts to findand study models of non-Fermi liquids, the general possibilities remain unknownand making contact between theory and experiment has proved difficult.

In this talk, Iwill describe our recent works attempting, through general reasoning, to findthe most universal statements that can be made about any metal, Fermi liquid ornot, even in the absence of any specific model. The key idea is to use"compressibility" as a proxy for metallicity. Compressibility refersto the ability of a system to support a continuously varying range of electrondensities without going through a phase transition (almost all metals seem tobe compressible in practice). I will give a general framework to understand theimplications of compressibility, relating it to powerful non-perturbativefield-theoretic concepts such as emergent symmetries and anomalies, and thendiscuss how to interpret the results conceptually.

Short Bio:

Dominicreceived his PhD from the University of California, Santa Barbara, in 2018.Following postdocs at MIT and Harvard, he has recently joined the faculty atthe Perimeter Institute for Theoretical Physics.


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