Magnetophonons & type-B Goldstones from hydrodynamics to holography

Abstract

We perform a detailed analysis of a large class of effective holographic models with broken translations at finite charge density and magnetic field. We exhaustively discuss the dispersion relations of the hydrodynamic modes at zero magnetic field and successfully match them to the predictions from charged hydrodynamics. At finite magnetic field, we identify the presence of an expected type-B Goldstone boson Re[ω] ∼ k 2 , known as magnetophonon and its gapped partner-the magnetoplasmon. We discuss their properties in relation to the effective field theory and hydrodynamics expectations. Finally, we compute the optical conductivities and the quasinormal modes at finite magnetic field. We observe that the pinning frequency of the magneto-resonance peak increases with the magnetic field, in agreement with experimental data on certain 2D materials, revealing the quantum nature of the holographic pinning mechanism.

Phase relaxation and pattern formation in holographic gapless charge density waves

“…The phase shifts, corresponding to a global shift symmetry, would result in φ I 0 → 0 + δϑ I . The corresponding hydrodynamic mode is a diffusive phason mode which has been observed directly in the QNMs spectrum [43,47,80] and which played a major role [46] in identifying the correct hydrodynamic description of these gravitational setups [44]. In presence of an explicit source, which in these models corresponds to deforming the axions-potential, this diffusive mode becomes damped with a relaxation rate given by Ω. Interestingly, even in these simple models, it follows the universal relation (6.2).…”

Magnetotransport and complexity of holographic metal-insulator transitions

“…7 When talking about pseudo-spontaneous breaking of translational invariance and holographic pinning mechanism (see e.g. [22,24]), it is convenient to keep m 2 explicitly in the action (2.1) and a typical choice of graviton mass term V (X) is given by…”

“…The AC conductivity in the presence of lattice symmetry breaking has been widely investigated in the literature, see e.g. [21,24,27,32,38,47] with homogeneous lattices and [34,36,[48][49][50] with inhomogeneous lattices.…”

“…in[10][11][12][13][14][15] 2. Despite a lot of work on linear axion models and generalizations, see e.g [17][18][19][20][21][22][23][24],. the physical nature of the dual field theories is not well understood yet[25,26].…”

Chiral hydrodynamics in strong external magnetic fields

“…Dispersion relations of hydrodynamic and non-hydrodynamic modes within the system under consideration in this work have been computed from quasinormal modes previously at weak magnetic fields of first order in the hydrodynamic derivative expansion [34]. Quasinormal modes of magnetic black branes were calculated in [34,[61][62][63]. In [58] dynamical gauge fields in the dual field theory are considered within a two-form field formalism which is distinct from ours.…”