Quantitative Raman measurements of the evolution of the Cooper-pairs density with doping in Bi2Sr2CaCu2O8+d superconductors

TL;DR

This study uses Raman spectroscopy to quantitatively analyze how the density of Cooper pairs in Bi2Sr2CaCu2O8+d superconductors changes with doping, revealing a competition with the pseudogap and differences from superfluid density.

Contribution

It provides the first quantitative evaluation of Cooper-pair density evolution with doping in Bi2Sr2CaCu2O8+d using Raman measurements, highlighting the competition with the pseudogap.

Findings

Loss of Cooper pairs in the antinodal region at low doping

Correlation between Cooper-pair loss and pseudogap formation

Distinct evolution of Cooper-pair density from superfluid density above p_c=0.2

Abstract

We report Raman measurements on Bi2Sr2CaCu2O8+d single crystals which allow us to quantitavely evaluate the doping dependence of the density of Cooper pairs in the superconducting state. We show that the drastic loss of Cooper pairs in the antinodal region as the doping level is reduced, is concomitant with a deep alteration of the quasiparticles dynamic above Tc and consistent with a pseudogap which competes with superconductivity. Our data also reveal that the overall density of Cooper pairs evolves with doping, distinctly from the superfluid density above the doping level pc=0.2.