The cuprate high temperature superconductors exhibit a pronounced trend in which the superconducting transition temperature, Tc, increases with the number of CuO2 planes, n, in the crystal structure. We compare the magnetic excitation spectrum of Bi2+xSr2−xCuO6+δ (Bi-2201) and Bi2Sr2Ca2Cu3O10+δ (Bi-2223), with n=1 and n=3 respectively, using Cu L3-edge resonant inelastic x-ray scattering (RIXS). Near the anti-nodal zone boundary we find the paramagnon energy in Bi-2223 is substantially higher than that in Bi-2201, indicating that multilayer cuprates host stronger effective magnetic exchange interactions, providing a possible explanation for the Tc vs.\ n scaling. In contrast, the nodal direction exhibits very strongly damped, almost non-dispersive excitations. We argue that this implies that the magnetism in the doped cuprates is partially itinerant in nature.
@article{arxiv.1409.2053,
title = {Itinerant effects and enhanced magnetic interactions in Bi-based multilayer cuprates},
author = {M. P. M. Dean and A. J. A. James and A. C. Walters and V. Bisogni and I. Jarrige and M. Huecker and E. Giannini and M. Fujita and J. Pelliciari and Y. Huang and R. M. Konik and T. Schmitt and J. P. Hill},
journal= {arXiv preprint arXiv:1409.2053},
year = {2015}
}