Electronic Raman scattering on out-of-plane disordered Bi2Sr2CaCu2O8+δ: How the pseudogap affects the superconducting Raman response.

We report Raman scattering measurements on Bi2Sr2CaCu2O8+δ single crystals with a different degree of out-of-plane disorder to examine the effect of Tc change on the the electronic Raman response at the optimal doping level. The Blg peak energies for lower Tc disordered samples are essentially independent of Tc. However, a further increase of Tc by minimizing the degree of out-of-plane disorder leads to a high-energy shift of the B1g peak. Interestingly, abrupt change of the B1g peak energy occurs when the the superconducting gap energy exceeds the pseudogap energy, which results in the recovery of superconductivity-dominated Raman response in B1g symmetry. It suggests that these anomalous properties of the antinodal electrons are a consequence of the unconventional superconducting state of the cuprates where superconductivity coexists with the pseudogap in the ground state. [ABSTRACT FROM AUTHOR]