Kinetics of information scrambling in correlated electrons: disorder-driven transition from shock-wave to FKPP dynamics

TL;DR

This paper develops a kinetic theory to study how disorder affects quantum information scrambling in correlated electrons, revealing a transition from shock-wave to FKPP wave dynamics as impurity scattering increases.

Contribution

It introduces a rigorous kinetic framework that identifies a disorder-driven transition in scrambling dynamics, connecting shock-wave and FKPP wave regimes in correlated metals.

Findings

Disorder slows down quantum information scrambling.

A transition from shock-wave to FKPP wave dynamics occurs at finite disorder.

The butterfly velocity is bounded by the Fermi velocity.

Abstract

Quenched disorder slows down the scrambling of quantum information. Using a bottom-up approach, we formulate a kinetic theory of scrambling in a correlated metal near a superconducting transition, following the scrambling dynamics as the impurity scattering rate is increased. Within this framework, we rigorously show that the butterfly velocity $v$ is bounded by the light cone velocity $v_{\rm lc }$ set by the Fermi velocity. We analytically identify a disorder-driven dynamical transition occurring at small but finite disorder strength between a spreading of information characterized at late times by a discontinuous shock wave propagating at the maximum velocity $v_{\rm lc}$, and a smooth traveling wave belonging to the Fisher or Kolmogorov-Petrovsky-Piskunov (FKPP) class and propagating at a slower, if not considerably slower, velocity $v$. In the diffusive regime, we establish the relation $v^2/\lambda_{\rm FKPP} \sim D_{\rm el}$ where $\lambda_{\rm FKPP}$ is the Lyapunov exponent set by the inelastic scattering rate and $D_{\rm el}$ is the elastic diffusion constant.