We present an explanation of the unusual peak/dip/hump features observed in photoemission experiments on Bi2212 at T ≪ Tc. We argue that the strong spin-fermion interaction combined with the feedback effect on the spin damping due to superconductivity yields a Fermi liquid form of the fermionic spectral function for ω < 2Δ where Δ is the maximum value of the superconducting gap, and a nonFermi liquid form for ω > 2Δ. In the Fermi liquid regime, the spectral function A(kF, ω) displays a quasiparticle peak at ω = Δ; in the nonFermi liquid regime it possesses a broad maximum at ω ≫ Δ. In between the two regimes, the spectral function has a dip at ω ∼ 2Δ.
- Fermi liquid
- Superconducting cuprate