Scanning Tunneling Spectroscopy of Lead - Substituted Bismuth Strontium Copper Oxide

The hole-doped cuprate Bi2-_Pb.Sr 2CulO 6+6 is doped with lead to the solubility limit of x = 0.38 and studied using STM/STS in the overdoped regime where T, < 2K. Despite the high lead content, residual supermodulations are observed in the BiO plane. In agreement with previous studies on (Pb,Bi)-2201, there is no separation of the sample into Pb-rich and Pb-poor domains, nor is there a spectral correlation with Pb location. Differential tunneling conductance is modeled using the van Hove scenario, wherein modulated regions are shown to have higher values of EVHS than flat regions. The consistency of parameters matching theoretical predictions to tunneling spectra suggest that EVHS describes a significant part of the density of states. Thesis Supervisor: Eric W. Hudson Title: Assistant Professor, Department of Physics