• Accepted Paper

ac fingerprints of 2D electron hydrodynamics: Superdiffusion and Drude weight suppression

Davis Thuillier and Thomas Scaffidi

Phys. Rev. Lett. - Accepted 21 July, 2026

DOI: https://doi.org/10.1103/p8sw-99rn

Abstract

Clean two-dimensional Fermi liquids are now known to exhibit an intermediate regime, between ballistic and Navier–Stokes transport, caused by the anomalously slow relaxation of parity-odd multipolar deformations of the Fermi surface. Here we show this anomaly extends to the dynamical realm. Starting from a microscopic numerical evaluation of the linearized electron–electron collision operator, we find that the finite-frequency nonlocal conductivity is controlled at low frequency by a single hydrodynamic pole, σ(q,ω)=𝒟(q)/(iω+η⋆qz), with dynamical exponent z=4/3 and superdiffusive viscosity η⋆. Remarkably, the pole residue itself is scale dependent and obeys 𝒟(q)∼q−α with α=1/3, so the dynamical properties are described by two separate exponents rather than one. We interpret the residue suppression using a Krylov-chain description of current relaxation: as q increases, the longest-lived quasinormal mode ceases to be a nearly pure current excitation and spreads over higher odd angular harmonics. Finally, we show that AC transport in narrow channels provides a direct experimental probe of these phenomena.

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