Magnetic excitations and phonons simultaneously studied by resonant inelastic x-ray scattering in optimally doped Bi1.5Pb0.55Sr1.6La0.4CuO6+delta

Magnetic excitations in the optimally doped high-T-c superconductor Bi1.5Pb0.55Sr1.6La0.4CuO6+delta (OP-Bi2201, T-c similar or equal to 34 K) are investigated by Cu L-3 edge resonant inelastic x-ray scattering (RIXS), below and above the pseudogap opening temperature. At both temperatures the broad spectral distribution disperses along the (1,0) direction up to similar to 350 meV at zone boundary, similar to other hole-doped cuprates. However, above similar to 0.22 reciprocal lattice units, we observe a concurrent intensity decrease for magnetic excitations and quasielastic signals with weak temperature dependence. This anomaly seems to indicate a coupling between magnetic, lattice, and charge modes in this compound. We also compare the magnetic excitation spectra near the antinodal zone boundary in the single layer OP-Bi2201 and in the bilayer optimally doped Bi1.5Pb0.6Sr1.54CaCu2O8+delta (OP-Bi2212, T-c similar or equal to 96 K). The strong similarities in the paramagnon dispersion and in their energy at zone boundary indicate that the strength of the superexchange interaction and the short-range magnetic correlation cannot be directly related to T-c, not even within the same family of cuprates.