Breakdown of Fermi liquid theory in topological multi-Weyl semimetals

TL;DR

This paper reveals that topological double- and triple-Weyl semimetals exhibit a breakdown of Fermi liquid theory due to their unique dispersion, leading to unconventional non-Fermi liquid behavior despite damping rates approaching zero.

Contribution

It demonstrates that the traditional criterion for Fermi liquid validity fails in these semimetals, showing a novel weaker-than-marginal violation caused by their special dispersion relations.

Findings

Quasiparticle residue vanishes despite damping rate approaching zero.

Spectral function and damping rate can be experimentally probed.

Coulomb interaction significantly alters density of states and conductivities.

Abstract

Fermi liquid theory works very well in most normal metals, but is found violated in many strongly correlated electron systems, such as cuprate and heavy-fermion superconductors. A widely accepted criterion is that, the Fermi liquid theory is valid when the interaction-induced fermion damping rate approaches zero more rapidly than the energy. Otherwise, it is invalid. Here, we demonstrate that this criterion breaks down in topological double-and triple-Weyl semimetals. Renormalization group analysis reveals that, although the damping rate of double- and triple-Weyl fermions induced by the Coulomb interaction approaches zero more rapidly than the energy, the quasiparticle residue vanishes and the Fermi liquid theory is invalid. This behavior indicates a weaker-than-marginal violation of the Fermi liquid theory. Such an unconventional non-Fermi liquid state originates from the special dispersion of double- and triple-Weyl fermions, and is qualitatively different from all the other Fermi-liquid and non-Fermi-liquid states. The predicted properties of the fermion damping rate and the spectral function can be probed by the angle-resolved photoemission spectroscopy. The density of states, specific heat, and conductivities are also calculated and analyzed after incorporating the corrections induced by the Coulomb interaction.