Signatures of Fermi surface reconstruction in Raman spectra of underdoped cuprates

TL;DR

This paper models Raman spectra in underdoped cuprates to identify signatures of Fermi surface reconstruction and pseudogap effects, aligning with experimental data and providing insights into the electronic structure.

Contribution

It introduces a model based on the resonating valence-bond spin-liquid to analyze Raman spectra, revealing signatures of Fermi surface reconstruction and pseudogap effects in underdoped cuprates.

Findings

Sharp rise in antinodal to nodal peak ratio below quantum critical point

Temperature dependence of B1g spectra indicates Fermi pocket confinement of the gap

Linear low energy B2g spectrum maintains d-wave form with an effective gap

Abstract

We have calculated the Raman B$_{1g}$ and B$_{2g}$ spectra as a function of temperature, as well as doping, for the underdoped cuprates, using a model based on the resonating valence-bond spin-liquid. We discuss changes in intensity and peak position brought about by the presence of a pseudogap and the implied Fermi surface reconstruction, which are elements of this model. Signatures of Fermi surface reconstruction are evident as a sharp rise in the doping dependence of the antinodal to nodal peak ratio which occurs below the quantum critical point. The temperature dependence of the B$_{1g}$ polarization can be used to determine if the superconducting gap is limited to the Fermi pocket, as seen in angle resolved photoemission spectroscopy, or extends beyond. We find that the slope of the linear low energy B$_{2g}$ spectrum maintains its usual d-wave form, but with an effective gap which reflects the gap amplitude projected on the Fermi pocket. Our calculations capture the main qualitative features revealed in the extensive data set available on the HgBa$_2$CuO$_{4+\delta}$ (Hg-1201) cuprate.