QUANTUM MATERIALS AND DEVICES SEMINARS: Landau`s Fermi liquids in disguise

Correlated metals, and sometimes even correlated insulators, often display non-Fermi liquid properties, like single-particle spectra lacking quasiparticles and very poor, or even absent, metallic charge transport,  coexisting with conventional Fermi liquid behaviour of thermal properties or quantum oscillations. That Janus-faced character likely entails the existence  of new paradigms of strongly interacting electrons, but, sometimes, it might simply indicate that the class of Landau`s Fermi liquids is broader and displays a richer physics than commonly believed.

Here, I will show that, contrary to the common belief, coherent `quasiparticles` also emerge approaching a Luttinger surface, i.e., the location within the Brillouin zone of the zeros of the single-particle Green`s function at zero energy  and temperature, just as they do approaching a Fermi surface, where the Green’s function has instead poles. That occurs despite the single-particle pseudogap at the Luttinger surface. The microscopic derivation  of Landau’s Fermi liquid theory, leading to the conventional expression of the low-frequency long-wavelength linear response functions, and thus of the uniform thermodynamic susceptibilities, works for  `quasiparticles`at a Luttinger surface just like it does for quasiparticles at a Fermi surface, For instance, `quasiparticles`at a Luttinger surface yield a standard linear in temperature specific heat, in striking contrast with the vanishing single-particle density of states.  Remarkably, Luttinger`s theorem entails that the number of `quasiparticles` at a Luttinger surface counts the number of physical holes,  while the number of quasiparticles at the Fermi surface counts the number of physical electrons.

I will end discussing the surprisingly reach physical behaviour that comes out of a toy self-energy vaguely inspired by the phenomenology of underdoped cuprates, and which admits a Luttinger surface either alone or coexisting with Fermi pockets, and thus unconventional `quasiparticles` coexisting or not with conventional ones.

M. Fabrizio, arXiv:2105.12528
M. Fabrizio, Physical Review B 102, 155122 (2020)
Host: Miguel A. Cazalilla

ZOOM: https://dipc-org.zoom.us/meeting/register/tZAqceGqrzMqE9fPWdhzaKxoIscCspVlFJ4Y

Online Seminar, Donostia International Physics Center


Michele Fabrizio, International School for Advanced Studies SISSA, Trieste, Italy

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