Phase-Coherent Drag of Plasmons in a 2D Flowing Fermi Liquid

Abstract

Collective modes in electron fluids feature phase-coherent drag response under a background carrier flow, resembling the optical Fizeau drag of photons by a moving medium. Time reversal breaking due to Fermi surface polarization by the flow results in nonreciprocity: collective modes acquire a ±𝑘 asymmetry in mode dispersion. This thesis explores plasmonic drag in two-dimensional electron fluids with a full account given to the Fermi-liquid interactions. These interactions are essential when the electron band is nonparabolic, as in graphene, giving rise to subtle “motional” Fermi-liquid effects which describe the flow-induced change in the quasiparticle velocities and interactions. These new Fermi-liquid effects can be represented as the flow-dependent interactions between quasiparticles on the Fermi surface deformed by the flow, in general not reducible to the standard Fermi-liquid parameters. A model of graphene Fermi-liquid predicts a substantial enhancement in the plasmon frequency shift, pointing to an opportunity to directly probe the motional Fermi-liquid effects in plasmonic near-field imaging experiments.