Angular Superdiffusion and Directional Memory in Two-Dimensional Electron Fluids

TL;DR

This paper reveals that two-dimensional electron fluids exhibit superdiffusive angular dynamics and directional memory, leading to long-lived excitations that challenge traditional hydrodynamic descriptions and can be experimentally observed.

Contribution

It introduces a microscopic model of superdiffusion and directional memory in 2D Fermi liquids, highlighting unique long-lived excitations and their implications for electron fluid behavior.

Findings

Identification of long-lived excitations not subject to T^2 dissipation

Development of a microscopic superdiffusion model on the Fermi surface

Prediction of experimental signatures via momentum-resolved tunneling

Abstract

We demonstrate that 2D Fermi liquids can support peculiar excitations that are not subject to Landau's $T^2$ dissipation. The long-lived excitations relax through correlated angular dynamics involving "lock-step" angular displacements along the Fermi surface occurring in collinear two-particle collisions, a surprising behavior that is unique to 2D systems. We develop a microscopic picture of the non-Brownian random walk, describing the angular dynamics as anomalous diffusion ("superdiffusion") on the Fermi surface. Strongly-correlated dynamics with directional memory, mediated by novel undamped excitations, dominates at moderately long times, pushing the onset of conventional hydrodynamics to abnormally large timescales. This exotic behavior can be directly probed by momentum-resolved tunneling techniques.