Transition from acoustic plasmon to electronic sound in graphene

Abstract

Fermi liquids respond differently to perturbations depending on whether their frequency is larger (collisionless regime) or smaller (hydrodynamic regime) than the inter-particle collision rate. This results in a different phase velocity between the collisionless zero sound and hydrodynamic first sound. We performed terahertz photocurrent nanoscopy measurements on graphene devices, with a metallic gate in close proximity to the sample, to probe the dispersion of propagating acoustic plasmons, the counterpart of sound modes in electronic Fermi liquids. We report the observation of a change in the plasmon phase velocity when the excitation frequency approaches the electron-electron collision rate. This first observation of the first sound mode in an electronic Fermi liquid is of fundamental interest and can enable novel terahertz emitter and detection implementations.

References in corpus (7)

• Highly confined low-loss plasmons in graphene-boron nitride heterostructures
• Drude weight, plasmon dispersion, and a.c. conductivity in doped graphene sheets
• Infrared Reflectance Spectrum of BN Calculated from First Principles
• Collective modes in interacting two-dimensional tomographic Fermi liquids
• Acoustic plasmons at the crossover between the collisionless and hydrodynamic regimes in two-dimensional electron liquids
• Electrical plasmon detection in graphene waveguides
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Cited by in corpus (6)

• Anomalous terahertz photoconductivity caused by the superballistic flow of hydrodynamic electrons in graphene
• Polaritonic Quantum Matter
• Vortices and backflow in hydrodynamic heat transport
• Interaction-mitigated Landau damping
• Enhanced Terahertz Photoresponse via Acoustic Plasmon Cavity Resonances in Scalable Graphene
• Strongly nonlinear Bernstein modes in graphene reveal plasmon-enhanced near-field magnetoabsorption