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Résumé |
Clean two-dimensional Fermi liquids are now known to exhibit an intermediate tomographic 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 that 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 with dynamical exponent z = 4/3. Remarkably, the pole residue itself is scale dependent and exhibits power-law decay with exponent 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 wavenumber 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 route to measuring the two exponents separately. |
