Comparing ARPES measurements on Bi2212 with penetration depth data, we show that a description of the nodal excitations of the d-wave superconducting state in terms of non-interacting quasiparticles is inadequate, and we estimate the magnitude and doping dependence of the Landau interaction parameter which renormalizes the linear T contribution to the superfluid density. Furthermore, although consistent with d-wave symmetry, the gap with underdoping cannot be fit by the simple coskx-cosky form, which suggests an increasing importance of long range interactions as the insulator is approached.
@article{arxiv.cond-mat/9812377,
title = {Superconducting Gap Anisotropy and Quasiparticle Interactions: a Doping Dependent ARPES Study},
author = {J. Mesot and M. R. Norman and H. Ding and M. Randeria and J. C. Campuzano and A. Paramekanti and H. M. Fretwell and A. Kaminski and T. Takeuchi and T. Yokoya and T. Sato and T. Takahashi and T. Mochiku and K. Kadowaki},
journal= {arXiv preprint arXiv:cond-mat/9812377},
year = {2009}
}