Suppression of shot noise in a dirty marginal Fermi liquid

In a series of papers [1,2,3], we have developed a quantum transport theory for dirty 2D non-Fermi liquids that exhibit Planckian dissipation and other marginal Fermi-liquid attributes. Our theory distinguishes quasiparticle and transport lifetimes, and predicts the survival of various quantum interference phenomena despite the strong dissipation of Planckian quasiparticles. Previous work addressed an elastic mechanism for linear-T resistivity [1] and how quantum interference mediated by virtual quantum-critical bosons can enhance superconductivity [2], despite a strong suppression of Cooper pairing due to the vanishing quasiparticle weight in the semiclassical approximation.

Here we study shot noise in a 2D dirty marginal Fermi liquid (MFL) driven out of equilibrium. We consider electrons with Planckian dissipation on the Fermi surface coupled to quantum-critical bosons in the presence of disorder. In the noninteracting and strong electron-boson drag limits, MFL effects disappear and our theory reproduces known results. For the case where the bosons remain in equilibrium, inelastic scattering strongly suppresses the noise by dissipating the injected electronic energy. Interestingly, we find that MFL effects do play a role in this regime, and give a weak enhancement of the noise, on top of the otherwise strong suppression.

Our results suggest that shot noise can be strongly suppressed in quantum-critical systems, and this scenario may be relevant to recent measurements in a heavy-fermion non-Fermi liquid [L. Chen et al., Science 382, 907 (2023)]. Our key finding is that the lack of well-defined quasiparticles itself does not appear to play a role in quieting the noise, and in fact induces a (very weak) opposite effect [3].