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NbCo is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Nb is bonded in a body-centered cubic geometry to eight equivalent Co atoms. All Nb–Co bond lengths are 2.67 Å. Co is bonded in a body-centered cubic geometry to eight equivalent Nb atoms.
NbCo(PbO3)2 is (Cubic) Perovskite-derived structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Nb5+ is bonded to six equivalent O2- atoms to form NbO6 octahedra that share corners with six equivalent CoO6 octahedra and faces with eight equivalent PbO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Nb–O bond lengths are 2.02 Å. Co3+ is bonded to six equivalent O2- atoms to form CoO6 octahedra that share corners with six equivalent NbO6 octahedra and faces with eight equivalent PbO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Co–O bond lengths are 2.01 Å. Pb2+ is bonded to twelve equivalent O2- atoms to form PbO12 cuboctahedra that share corners with twelve equivalent PbO12 cuboctahedra, faces with six equivalent PbO12 cuboctahedra, faces with four equivalent NbO6 octahedra, and faces with four equivalent CoO6 octahedra. All Pb–O bond lengths are 2.84 Å. O2- is bonded in a linear geometry to one Nb5+, one Co3+, and four equivalent Pb2+ atoms.
While electron-phonon coupling (EPC) is crucial for Cooper pairing in conventional superconductors, its role in high-Tc superconducting cuprates is debated. Here, using resonant inelastic x-ray scattering at the oxygen K edge, we study the EPC in Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) and Nd 1+x Ba 2-x Cu 3 O 7-δ (NBCO) at different doping levels ranging from heavily underdoped (p=0.07) to overdoped (p=0.21). We analyze the data with a localized Lang-Firsov model that allows for the coherent excitations of two phonon modes. While electronic band dispersion effects are non-negligible, we are able to perform a study of the relative values of EPC matrix elements in these cuprate families. In the case of NBCO, the choice of the excitation energy allows us to disentangle modes related to the CuO chains and the CuO 2 planes. Combining the results from the two families, we find the EPC strength decreases with doping at q∥=(-0.25, 0) r.l.u., but has a nonmonotonic trend as a function of doping at smaller momenta. This behavior is attributed to the screening effect of charge carriers. We also find that the phonon intensity is enhanced in the vicinity of the charge-density-wave excitations while the extracted EPC strength appears to be less sensitive to their proximity. By performing a comparative study of two cuprate families, we are able to identify general trends in the EPC for the cuprates and provide experimental input to theories invoking a synergistic role for this interaction in d -wave pairing.