Charge density response in layered metals: retardation effects, generalized plasma waves and their spectroscopic signatures

Abstract

Transverse plasma polaritons and longitudinal plasmons describe the propagation of light-matter modes in an isotropic metal. However, in a layered metal the anisotropy of the bare electromagnetic response mixes the longitudinal and transverse excitations, making the distinction between polariton and plasmon blurred at small wavevectors, where retardation effects of the electromagnetic interactions become quantitatively relevant. In the usual Kubo approach for the linear response, this effect appears as a mixing between the density and the transverse current fluctuations, that requires to revise the standard RPA approach for density correlations where only the instantaneous Coulomb potential is included. In this paper we derive the general expression for the density and current correlation functions at long wavelength in a layered metal, showing that below a crossover scale set by the anisotropy of the plasma frequencies retardation effects make the dispersion of the generalized plasma modes different from the standard RPA result. In addition, the mixed longitudinal and transverse nature of these excitations reflects in a double-peak structure for the density response, that can be eventually accessed by means of high-momentum resolution electron-energy-loss or X-rays spectroscopies.

arXiv comment22 pages, 3 figures

References in corpus (27)

• Optical excitations in electron microscopy
• Polaritons in layered 2D materials
• Resonant Inelastic X-ray Scattering Studies of Elementary Excitations
• Terahertz Josephson plasma waves in layered superconductors: spectrum, generation, nonlinear, and quantum phenomena
• Position and momentum mapping of vibrations in graphene nanostructures in the electron microscope
• Three dimensional collective charge excitations in electron-doped cuprate superconductors
• Anomalous density fluctuations in a strange metal
• Transverse optical plasmons in layered superconductors
• Electronic Collective Modes and Superconductivity in Layered Conductors
• Detection of Acoustic Plasmons in Hole-Doped Lanthanum and Bismuth Cuprate Superconductors Using Resonant Inelastic X-Ray Scattering
• Plasmons in strongly correlated systems: spectral weight transfer and renormalized dispersion
• Measurement of the dynamic charge response of materials using low-energy, momentum-resolved electron energy-loss spectroscopy (M-EELS)
• Collective Charge Excitations of Strongly Correlated Electrons, Vertex Corrections and Gauge Invariance
• Damping mechanism for the strongly renormalized $c$-axis charge transport in high-$T_c$ cuprate superconductors
• Doping evolution of the charge excitations and electron correlations in electron-doped superconducting La${}_{2-x}$Ce${}_x$CuO${}_4$
• Crossover of Charge Fluctuations across the Strange Metal Phase Diagram
• Optical Properties of Layered Superconductors near the Josephson Plasma Resonance
• Plasmon excitations in layered high-Tc cuprates
• Parametric resonance of Josephson plasma waves: A theory for optically amplified interlayer superconductivity in YBa${}_2$Cu${}_3$O${}_{6+x}$
• Acoustic plasmons and conducting carriers in hole-doped cuprate superconductors
• Non-linear Terahertz Driving of Plasma Waves in Layered Cuprates
• Origin of the high-energy charge excitations observed by resonant inelastic x-ray scattering in cuprate superconductors
• Gapped collective charge excitations and interlayer hopping in cuprate superconductors
• Generalized plasma waves in layered superconductors
• Generalized Josephson plasmons in bilayer superconductors
• Probing the bulk plasmon continuum of layered materials through electron energy loss spectroscopy in a reflection geometry
• Jamming and Unusual Charge Density Fluctuations of Strange Metals

Cited by in corpus (3)

• Investigating Josephson plasmons in layered cuprates via nonlinear terahertz spectroscopy
• Ghost Josephson plasmon in bilayer superconductors
• Optical absorption in tilted geometries as an indirect measurement of longitudinal plasma waves in layered cuprates