Charge critical fluctuations in cuprates: Isotope effect, pseudogap, conductivity, and Raman spectroscopy

TL;DR

This paper investigates how charge fluctuations near a quantum critical point influence optical and Raman spectra in high-temperature cuprate superconductors, revealing directional dependencies and coupling strengths.

Contribution

It demonstrates the direct impact of charge collective fluctuations on optical and Raman responses, confirming finite wavevector order near optimal doping in cuprates.

Findings

Charge fluctuations affect optical absorption and Raman spectra.

The excitation of charge modes depends on wavevector and photon polarization.

Evidence supports finite wavevector order at the quantum critical point.

Abstract

Within the stripe quantum critical point theory for high T_c superconductors, we point out that there is a direct contribution of charge collective fluctuations to the optical absorption and to the Raman spectra. In this latter case, we find that the critical charge collective modes can or can not be excited depending on the direction of their wavevector and on the polarization of the incoming and outgoing photons. This indicates a marked distinction between quasiparticles which are strongly and weakly coupled to critical collective modes and provides a direct confirmation that the order associated to the quantum critical point near optimal doping of cuprates occurs at finite wavevectors.