Dynamical scaling and Planckian dissipation due to heavy-fermion quantum criticality

TL;DR

This paper investigates the dynamical scaling and Planckian dissipation at a heavy-fermion quantum critical point using 2CDMFT, revealing SYK-like slow dynamics, strange-metal behavior, and matching experimental optical conductivity results.

Contribution

It introduces a scaling Ansatz for the quantum critical behavior of heavy-fermion systems, demonstrating intrinsic strange-metal fixed points with SYK-like dynamics driven by strong vertex contributions.

Findings

Observation of $/T$ scaling in susceptibility

Identification of SYK-like slow dynamics

Matching experimental optical conductivity data

Abstract

We study dynamical scaling associated with a Kondo-breakdown quantum critical point (KB-QCP) of the periodic Anderson model, treated by two-site cellular dynamical mean-field theory (2CDMFT). In the quantum critical region, the staggered spin exhibits SYK-like slow dynamics and its dynamical susceptibility shows $\omega/T$ scaling. We propose a scaling Ansatz that describes this behavior. It also implies Planckian dissipation for the longest-lived excitations. The current susceptibility follows the same scaling ansatz, leading to strange-metal scaling. This demonstrates that the KB-QCP described by 2CDMFT is an intrinsic (i.e., disorder-free) strange-metal fixed point. Surprisingly, the SYK-like dynamics and scaling are driven by strong vertex contributions to the susceptibilities. Our results for the optical conductivity match experimental observations on YbRh${}_2$Si${}_2$ and CeCoIn${}_5$.