Theory of the leading edge gap in underdoped cuprates

We present the theory of the leading edge gap in the normal state of underdoped high-T_c materials. The consideration is based on a magnetic scenario for cuprates. We show that as doping decreases, the increasing interaction with paramagnons gives rise to a near destruction of the quasiparticle peak near (0, π) and symmetry related points. We then solve the d-wave pairing problem and show that the actual T_c decreases with the strength of the coherent quasiparticle peak, but the precursors to d-wave state exist above T_c even for fully incoherent quasiparticles.