A simple theory for high ΔTc ratio in d-wave superconductors

We investigate a simple explanation for the high maximum gap to Tc ratio found experimentally in high Tc compounds. We ascribe this observation to the lowering of Tc by boson scattering of electrons between parts of the Fermi surface with opposite sign for the order parameter. We study the simplest possible model within this picture. Our quantitative results show that we can account for experiment for a rather small value of the coupling constant, all the other ingredients of our model being already known to exist in these compounds. A striking implication of this theory is the fairly high value of the critical temperature in the absence of boson scattering.