Evidence of strong correlations at the van Hove singularity in the   scanning tunneling spectra of superconducting   Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} single crystals
  We present realistic multiband calculations of scanning tunneling spectra in Bi_{2}Sr_{2}CaCu_{2} O_{8+\delta} over a wide doping range. Our modeling incorporates effects of a competing pseudogap and pairing gap as well as effects of strong electronic correlations, which are included by introducing self-energy corrections in the one-particle propagators. The calculations provide a good description of the two-gap features seen in experiments at low energies and the evolution of the Van Hove singularity (VHS) with doping, and suggest a possible quantum critical point near the point where the VHS crosses the Fermi level. 
Jouko Nieminen, Ilpo Suominen, Tanmoy Das, R. S. Markiewicz, A. Bansil
cond-mat.supr-con