Holographic Acoustic Phonons as the secret black hole Zero Sound source of quantum gravitons

 We present a class of holographic massive gravity models that realize a spontaneous breaking of translational symmetry – they exhibit transverse phonon modes whose speed relates to the elastic shear modulus according to elasticity theory. Massive gravity theories thus emerge as versatile and convenient theories to model generic types of translational symmetry breaking: explicit, spontaneous and a mixture of both. The nature of the breaking is encoded in the radial dependence of the graviton mass. As an application of the model, we compute the temperature dependence of the shear modulus and find that it features a glass-like melting transition

 Holographic Phonon research launched in 2017 and cited 41 times

 gapped transverse phonons were identified,
with the size of the gap being directly related to the
asymptotic behaviour of the graviton mass.

 a spontaneous symmetry breaking (SSB) of transla-
tions and provide a realization of massless phonons, i.e.
the corresponding Goldstone bosons. The resulting gap-
less modes show properties indentical to the transverse
phonons in solids

This is also called "Zero Sound." 

Zero sound is the name given by Lev Landau to the unique quantum vibrations in quantum Fermi liquids.

a fluctuation in space and time of the quasiparticles' momentum distribution function.

 Back to the HOlographic Phonon claim:

the first time that transverse phonons
are realized within holography, with a sharp and clear
relation to the elastic moduli as dictated by standard
elasticity theory

Depending on the direction of propagation with respect to the
deformation of the medium they can be classified into
longitudinal and transverse phonons; in this letter we
shall focus on the latter. The presence of propagating
transverse phonons, also called the shear sound, is a
characteristic property of solids and provides a clear
physical distinction from fluids.

Corroboration of Holographic Phonons 

 In this paper, we show that a simple generalization of the holographic axion model can realize spontaneous breaking of translational symmetry by considering a special gauge-axion higher derivative term. The finite real part and imaginary part of the stress tensor imply that the dual boundary system is a viscoelastic solid. By calculating quasi-normal modes and making a comparison with predictions from the elasticity theory, we verify the existence of phonons and pseudo-phonons, where the latter is realized by introducing a weak explicit breaking of translational symmetry, in the transverse channel. Finally, we discuss how the phonon dynamics affects the charge transport.

https://link.springer.com/article/10.1007/JHEP10(2019)064 

 Finally, we extend the analysis of the collective longitudinal modes beyond the hydrodynamic limit by displaying the dynamics of the higher quasi-normal modes at large frequencies and momenta.