  Tunneling measurements have been carried out on heavily underdoped, slightly
overdoped and partially Ni-substituted Bi2212 single crystals by using a
break-junction technique. We find that in-plane tunneling spectra below Tc are
the combination of incoherent part from the pseudogap and coherent
quasiparticle peaks. There is a clear correlation between the magnitude of the
pseudogap and the magnitude of the superconducting gap in Bi2212. The analysis
of the data suggests that the tunneling pseudogap in Bi2212 is predominantly a
charge-density-wave gap on dynamical charge stripes. The tunneling
characteristics corresponding to the quasiparticle peaks are in excellent
agreement with theoretical predictions made for a quasi-one dimensional
topological-excitation liquid. In addition, the analysis of data measured by
different techniques shows that the phase coherence along the c-axis is
established at Tc due to spin fluctuations in local antiferromagnetic domains
of CuO2 planes.
