Unconventional properties of superconducting cuprates

We present an explanation of the unusual peak/dip/hump features observed in photoemission experiments on Bi2212 at T much less than T-c. We argue that the strong spin-fermion interaction combined with the feedback effect on t he spin damping due to superconductivity yields a Fermi liquid form of the fermionic spectral function for omega < 2 Delta where Delta is the maximum value of the superconducting gap, and a nonFermi liquid form for omega > 2 Delta. In the Fermi liquid regime, the spectral function A(k(F), omega) dis plays a quasiparticle peak at omega = Delta; in the nonFermi liquid regime it possesses a bread maximum at omega much greater than Delta. In between t he two regimes, the spectral function has a dip at omega similar to 2 Delta . (C) 1999 Elsevier Science B.V. All rights reserved.