An electron-boson glue function derived from electronic Raman scattering

Raman scattering cross sections depend on photon polarization. In the cuprates, nodal and antinodal directions are weighted more strongly in B-2g and B-1g symmetries, respectively. On the other hand, in angle-resolved photoemission spectroscopy (ARPES), electronic properties are measured along well-defined directions in momentum space rather than their weighted averages being taken. In contrast, the optical conductivity involves a momentum average over the entire Brillouin zone. Newly measured Raman response data on high-quality Bi2Sr2CaCu2O8+delta single crystals up to high energies have been inverted using a modified maximum entropy inversion technique to extract from B-1g and B-2g Raman data corresponding electron-boson spectral densities (glue), and these are compared to the results obtained with known ARPES and optical inversions. We find that the B-2g spectrum agrees qualitatively with nodal direction ARPES while the B-1g results look more like the optical spectrum. A large peak around 30-40 meV in B-1g and a much less prominent one in B-2g are taken as support for the importance of (pi, pi) scattering at this frequency.