Unconventional properties of superconducting cuprates

Abstract

We present an explanation of the unusual peak/dip/hump features observed in photoemission experiments on Bi2212 at T⪡ T c. 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<2 Δ where Δ is the maximum value of the superconducting gap, and a nonFermi liquid form for ω>2 Δ. In the Fermi liquid regime, the spectral function A(k F , 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∼2 Δ.