Acoustic plasmons at the crossover between the collisionless and
hydrodynamic regimes in two-dimensional electron liquids
PHYSICAL REVIEW B, (2019)DOI: 10.1103/PhysRevB.99.144307
Abstract
Hydrodynamic flow in two-dimensional electron systems has so far been
probed only by dc transport and scanning gate microscopy measurements.
In this work we discuss theoretically signatures of the hydrodynamic
regime in near-field optical microscopy. We analyze the dispersion of
acoustic plasmon modes in two-dimensional electron liquids using a
nonlocal conductivity that takes into account the effects of
(momentumconserving) electron-electron collisions, (momentum-relaxing)
electron-phonon and electron-impurity collisions, and many-body
interactions beyond the celebrated random phase approximation. We derive
the dispersion and, most importantly, the damping of acoustic plasmon
modes and their coupling to a near-field probe, identifying key
experimental signatures of the crossover between collisionless and
hydrodynamic regimes.