Systematics of electronic structure and interactions in Bi₂Sr₂Ca_n-1Cu_nO_2n+4 (n=1-3) by angle-resolved photoemission spectroscopy

We have performed systematic angle-resolved photoemission spectroscopy on the high-T_c superconducting family of Bi₂Sr₂Ca_n-1Cu_nO_2n+4 (n = 1-3). In addition to the generic features of the large Fermi surface and d-wave superconducting gap, we have found that there exists a scaling of the doping dependence of the energy gap. Moreover, comparison of the nodal dispersion in the superconducting state shows that the "kink" (the sudden change of band dispersion), while occurring at a similar binding energy, becomes more pronounced with increasing layer number n, indicating stronger coupling between electrons and a collective mode.