Spectral function of superconducting cuprates near optimal doping

We argue that the unusual peak-dip-hump features observed in photoemission experiments on Bi2212 at T much less than T-c can be explained by the interaction of the fermionic quasiparticles with overdamped spin fluctuations. We show that the strong spin-fermion interaction combined with the feedback effect on the spin damping due to superconductivity yields the fermionic spectral function A(k(F), omega) which simultaneously displays a quasiparticle peak at w = Delta and a broad maximum thump) at w much greater than Delta. In between the two regimes, the spectral function has a dip at w similar to 2 Delta. We argue that our theory also explains the tunneling data. [S0031-9007(98)07732-1].