Tunneling density of states of high T_c superconductors d-wave BCS model   vs. SU(2) slave boson model
  Motivated by recent experimental measurements of the tunneling characteristics of high T_{c} materials using scanning tunneling spectroscopy, we have calculated the IV and differential conductance curves in the superconducting state at zero temperature. Comparing the two results obtained via BCS-like d-wave pairing and the SU(2) slave boson approach, we find that the slave-boson model can explain the asymmetric background observed in experiments. The slave-boson model also predicts that the height of the conductance peak relative to the background is proportional to the hole doping concentration $x$, at least for under-doped samples. We also observe the absence of the van Hove singularity, and comment on possible implications. 
Walter Rantner and Xiao-Gang Wen