  The plasmon is a ubiquitous collective mode in charged liquids. Due to the
long-range Coulomb interaction, the massless zero sound mode of the neutral
system acquires a finite plasmon frequency in the long-wavelength limit. In the
zero-temperature state of conventional metals -- the Fermi liquid -- the
plasmon lives infinitely long at long wavelength when the system is
(effectively) translationally invariant. In contrast, we will show that in
strongly entangled strange metals the protection of zero sound fails at finite
frequency and plasmons are always short lived regardless of their wavelength.
Computing the explicit plasmon response in holographic strange metals as an
example, we show that decay into the quantum critical continuum replaces Landau
damping and this happens for any wavelength.

Strongly Correlated Electrons;High Energy Physics - Theory