Evolution of Magnetic and Superconducting Fluctuations with Doping of High-Tc

Electronic Raman scattering from high- and low-energy excitations was studied as a function of temperature, extent of hole doping, and energy of the incident photons in Bi2Sr2CaCu2O86d superconductors. For underdoped superconductors, short-range an-tiferromagnetic (AF) correlations were found to persist with hole doping, and doped single holes were found to be incoherent in the AF environment. Above the supercon-ducting (SC) transition temperature Tc, the system exhibited a sharp Raman resonance of B1g symmetry and energy of 75 millielectron-volts and a pseudogap for electron-hole excitations below 75 millielectron-volts, a manifestation of a partially coherent state forming from doped incoherent quasi particles. The occupancy of the coherent state increases with cooling until phase ordering at Tc produces a global SC state. The normal state properties of doped cu-prate high-temperature superconductors are markedly different from those of conven-tional metals and are usually viewed as man-ifestations of strong electron-electron corre