Strange metal behaviour from charge density fluctuations in cuprates

Abstract

Besides the mechanism responsible for high critical temperature superconductivity, the grand unresolved issue of the cuprates is the occurrence of a strange metallic state above the so-called pseudogap temperature T*. Even though such state has been successfully described within a phenomenological scheme, the so-called Marginal Fermi-Liquid theory, a microscopic explanation is still missing. However, recent resonant X-ray scattering experiments identified a new class of charge density fluctuations characterized by low characteristic energies and short correlation lengths, which are related to the well-known charge density waves. These fluctuations are present over a wide region of the temperature-vs-doping phase diagram and extend well above T*. Here we investigate the consequences of charge density fluctuations on the electron and transport properties and find that they can explain the strange metal phenomenology. Therefore, charge density fluctuations are likely the long-sought microscopic mechanism underlying the peculiarities of the metallic state of cuprates.

Dissipation-driven Strange Metal Behavior

“…This calculation follows closely the approach used in Ref. 20 for the fermion tight-binding dispersion, the calculation of the electron scattering rate, and the solution of the Boltzmann equation. Regarding the parameters of the fluctuations, these were extracted from RXS experiments on a NdBa 2 Cu 3 O 7−y sample, consistently leading to a deviation from linearity below T F L ≈ 100 K in agreement with the resistivity data.…”

“…The concomitant occurrence of a broad peak witnesses for the presence of dynamical charge density fluctuations with rather short correlation length and broad momentum distribution. These abundant charge density fluctuations are available to isotropically scatter the quasiparticles over a broad range of momenta and no clear distinction can be done between hot and cold Fermi surface regions 20 . This was the first explicit example that a quenched criticality with a finite ordering wave vector q c can still give rise to strong but isotropic scattering, thereby bypassing the problem that in standard hot spot models most electrons contribute with a ∼ T 2 scattering rate to transport 7 .…”

Revival of Charge Density Waves and Charge Density Fluctuations in Cuprate High-Temperature Superconductors

“…) where is the CDW field (or fluctuation mode) and is the coefficient of the Landau damping term . From an inspection of Equation (7), it is natural to define a characteristic energy for each q:…”

“…The very broad spectrum (BP) of CDFs allows us [7] to approach the old standing problem of strange metal (SM) of cuprates, in particular the anomalous linear in T resistivity ρ(T)∼T from T > T* up to the highest attained temperatures. One of the prerequisites identified in the marginal FL phenomenological theory [62] to reproduce the strange metal is the presence of a strong isotropic scattering channel for the Fermi quasiparticles with all states on the Fermi surface nearly equally affected.…”

“…My aim is to retrace the line we followed over the years in Rome to produce a scenario of the physics of cuprates, for a recent review see [5]. I proceed through the years to end up with two recent contributions [6,7] produced with S. Caprara, M. Grilli and G. Seibold in a collaboration with the experimental group of the Politecnico of Milano on resonant X-ray scattering (RXS) (G. Ghiringhelli, L. Braicovich, R. Arpaia, among others) in which charge density fluctuations (CDFs) are thoroughly investigated leading to a deeper understanding of the physics of these systems. I have no claim of completeness; I only follow my line of reasoning for which no one else is responsible even though I am deeply indebted to Alex Müller for his continuous support in the first fifteen years of my research activity in this field and to all my collaborators throughout the years.…”