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Fermi surfaces large and small: unifying theories of the Anderson lattice and Hubbard models

Date and Time: Tuesday, September 21, 2021, 01:30pm -
Location: Zoom

Speaker: Subir Sachdev (Harvard U./ Institute for Advanced Study, Princeton)

The Luttinger theorem is a fundamental constraint on the structure of metallic phases of strongly correlated systems. Fermi surfaces which obey the Luttinger theorem are often referred to as “large”. However, it is possible to have “small” Fermi surfaces with electron-like quasiparticles, in certain metallic states (sometimes called FL*) which evade the Luttinger theorem using emergent gauge fields. I will review theories of small and large Fermi surfaces on the Anderson lattice (and the closely related Kondo lattice), and discuss their application to the heavy fermion compounds.

Then I will describe a new approach to transferring these insights to the single-band Hubbard model, and the physics of the cuprates. The key idea is to avoid fractionalizing the electron, and to instead fractionalize a paramagnon into a pair of ancilla qubits. This leads to a theory of a pseudogap metal as a FL* state, and of the quantum phase transition from FL* to an ordinary Fermi liquid, in a single band model.

Host:  Piers Coleman

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