Electron spectroscopy study of BSCCO high-temperature superconductors

Since the discovery of High-Tc superconductors, there has been a very strong effort to understand the electron dynamics and the pairing mechanism in these materials.; We present Photoemission Electron Spectroscopy (PES) data on {dollar}rm Bisb2Srsb{lcub}1.9{rcub}Prsb{lcub}0.1{rcub}CuOsb{lcub}6+delta{rcub}.{dollar} This was compared and contrasted with {dollar}rm Bisb2Srsb2CaCusb2Osb{lcub}8+delta{rcub}.{dollar} We carried out angle-integrated photoemission experiments which revealed the higher relative density of states in {dollar}rm Bisb2Srsb2CaCusb2Osb{lcub}8+delta{rcub}{dollar} than in {dollar}rm Bisb2Srsb{lcub}1.9{rcub}Prsb{lcub}0.1{rcub}CuOsb{lcub}6+delta{rcub}{dollar} at the Fermi level. We also carried out preliminary band mapping of {dollar}rm Bisb2Srsb{lcub}1.9{rcub}Prsb{lcub}0.1{rcub}CuOsb{lcub}6+delta{rcub}.{dollar} We observed strong matrix elements effects in the photoemission spectra. We fitted the extracted dispersive feature to the functional form predicted by Fermi liquid theory. The fits yielded a large value for the self-energy constant. We also used resonant photoemission to show why the addition of Pr did not affect the superconductivity in the BSCCO system unlike the case in YBCO.; We also present temperature-dependent Electron Energy Loss Spectroscopy (EELS) measurements on {dollar}rm Bisb2Srsb2CaCusb2Osb{lcub}8+delta{rcub}.{dollar} The experiment was specifically designed to probe the superconducting Cu-O layers of the {dollar}rm Bisb2Srsb2CaCusb2Osb{lcub}8+delta{rcub}{dollar} material. The experiment and the necessary measurement electronics were all built as part of the research leading up to this thesis. The total energy resolution of the experiment was 0.25 eV and was limited by the energy spread of the non-monochromatic incident beam. The pre-amplifier that was designed and built as part of this work could detect currents down to 10 fA. We carried out the Medium Energy Electron Energy Loss Spectroscopy experiment in reflection geometry on {dollar}rm Bisb2Srsb2CaCusb2Osb{lcub}8+delta{rcub}.{dollar} We also present optical thermal difference reflectance (TDR) measurements. We see a clear correspondence between the plasmon and the interband transition observed in the EELS and TDR spectra. Furthermore, we observe directly the charge-transfer excitation at 1.7 eV, which has been deduced by modeling the TDR data on a number of the cuprates in the superconducting state. The charge-transfer excitation is a weakly dipole allowed transition and thus not observable by direct optical measurements in the cuprates. The data strongly suggests that this charge-transfer excitation is involved in the pairing interaction.