Planckian Metal at a Doping-Induced Quantum Critical Point

TL;DR

This paper numerically investigates a model of interacting electrons near a doping-induced quantum critical point, revealing non-Fermi liquid behavior with Planckian dissipation, $ ext{ω/T}$ scaling, and SYK-like spin dynamics.

Contribution

It demonstrates the existence of a quantum critical point with non-Fermi liquid properties, including Planckian behavior and particle-hole asymmetry, in a doped electron model.

Findings

Identification of a quantum critical point separating metallic phases.

Observation of $T$-linear Planckian behavior in the non-Fermi liquid phase.

Discovery of $ ext{ω/T}$ scaling with particle-hole asymmetry.

Abstract

We numerically study a model of interacting spin-$1/2$ electrons with random exchange coupling on a fully connected lattice. This model hosts a quantum critical point separating two distinct metallic phases as a function of doping: a Fermi liquid phase with a large Fermi surface volume and a low-doping phase with local moments ordering into a spin-glass. We show that this quantum critical point has non-Fermi liquid properties characterized by $T$-linear Planckian behavior, $\omega/T$ scaling and slow spin dynamics of the Sachdev-Ye-Kitaev (SYK) type. The $\omega/T$ scaling function associated with the electronic self-energy is found to have an intrinsic particle-hole asymmetry, a hallmark of a `skewed' non-Fermi liquid.