Density of States Driven Anisotropies Induced by Momentum Decoupling in High-Tc Superconductors

Momentum decoupling arises when small momentum transfer processes dominate the electron-phonon scattering and implies that anisotropies in superconductivity are driven by the anisotropies of the density of states. Considering an isotropic s-wave interaction in the momentum decoupling regime we give a natural simultaneous explanation to various aspects of ARPES and tunnel experiments on $Bi_2Sr_2CaCu_2O_8$, including the correlation of gap magnitude and visibility of the dip above the gap, the enhancement of anisotropy with temperature, the presence of gap minima away from the $\Gamma-X$ direction and a gap maximum in the $\Gamma-X$ direction, the similarity of tunnel and ARPES spectra in the $\Gamma-\bar{M}$ direction and the asymmetry in the SIN tunnel spectra where the dip structure is present only at negative sample bias.