Incoherent hydrodynamics and density waves

We study a holographic model where translations are both spontaneously and explicitly broken, leading to the presence of (pseudo)-phonons in the spectrum. The weak explicit breaking is due to two independent mechanisms: a small source for the condensate itself and additional linearly space-dependent marginal operators. The low energy dynamics of the model is described by Wigner crystal hydrodynamics. In absence of a source for the condensate, the phonons remain gapless, but momentum is relaxed. Turning on a source for the condensate damps and pins the phonons. Finally, we verify that the universal relation between the phonon damping rate, mass and diffusivity reported in [1] continues to hold in this model for weak enough explicit breaking.1 These holographic homogeneous models inspired analogous constructions [20] which account for the translation-breaking dynamics in a purely field-theoretical context. For a generalization of such constructions to inhomogeneous case see [21]. 2 The pinning frequency can also be written more intuitively as ω o = c ⊥ k o with k o ≡ m the inverse length scale defined by the phonon mass and c ⊥ ≡ G/χ P P the shear sound velocity. 10 Based on private communication with the authors of [46] and [48].

Section: Introductionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 80%

Section: )mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Gapless and gapped holographic phonons

Amoretti

Areán

Goutéraux

et al. 2020

“…It is straightforward to understand the physical meaning of these modes [18]. In standard hydrodynamics [19], the sound mode originates from the coupled dynamics of the energy density and longitudinal momentum fluctuations.…”

Section: )mentioning

confidence: 99%

Charge density response and fake plasmons in holographic models with strong translation symmetry breaking

Andrade¹,

Krikun²,

Romero-Bermúdez³

2019

We study the charge density response in holographic models with explicit translation symmetry breaking which is relevant in the IR; in particular, we focus on Q-lattices and the Bianchi VII helix. We show that the hydrodynamic sound mode is removed from the spectrum due to the strong momentum relaxation and therefore, the usual treatment of the plasmon as Coulomb-dressed zero sound does not apply. Furthermore, the dominant coherent modes in the longitudinal channel, which control the neutral density-density correlator, are the diffusive modes. We show these modes are strongly suppressed when the boundary Coulomb interaction is turned on. This renders the low frequency charge density response spectrum completely incoherent and featureless.At intermediate frequencies, we observe a broad feature -the fake plasmonin the dressed correlator, which could be confused with an overdamped plasmon. However, its gap is set by the scale of translation symmetry breaking instead of the plasma frequency. This broad feature originates from the non-hydrodynamic sector of the holographic spectrum, and therefore, its behaviour, typical of strongly correlated quantum critical systems with holographic duals, deviates from the standard Fermiliquid paradigm.

Phase relaxation and pattern formation in holographic gapless charge density waves

Andrade

Baggioli

Krikun

2021

We study the dynamics of spontaneous translation symmetry breaking in holographic models in presence of weak explicit sources. We show that, unlike conventional gapped quantum charge density wave systems, this dynamics is well characterized by the effective time dependent Ginzburg-Landau equation, both above and below the critical temperature, which leads to a “gapless” algebraic pattern of metal-insulator phase transition. In this framework we elucidate the nature of the damped Goldstone mode (the phason), which has earlier been identified in the effective hydrodynamic theory of pinned charge density wave and observed in holographic homogeneous lattice models. We follow the motion of the quasinormal modes across the dynamical phase transition in models with either periodic inhomogeneous or helical homogeneous spatial structures, showing that the phase relaxation rate is continuous at the critical temperature. Moreover, we find that the qualitative low-energy dynamics of the broken phase is universal, insensitive to the precise pattern of translation symmetry breaking, and therefore applies to homogeneous models as well.