Temperature and pressure Raman studies of mercurocuprate superconductors and oligo(para-phenylene) materials

Temperature and pressure dependence of the Raman spectra of both Hg1201 high T_c superconductor and Oligo(Para-Phenylene) materials were presented. For Hg1201 superconductors, detailed temperature and pressure behaviors of the apical O(2) mode were investigated. We found that the temperature behavior of the apical O(2) mode exhibits three distinct temperature ranges between 10 to 300K. In the low temperature range, in which Hg1201 is in a superconducting state, the frequency of apical O(2) mode increases and it asymmetry increases with increasing temperature; in the high temperature range (∼200 to 300K), the temperature behavior of apical O(2) mode is the same as in ordinary materials. However, in the intermediate temperature range, the temperature behavior of apical O(2) mode is unusual. We conjecture that this behavior is due to the reordering of O(3) within this temperature range. Our pressure study of Hg1201 also provides evidence that the apical O(2) mode of Hg1201 is strongly related to the superconductivity in the material, as evidenced by the manner in which it responds to changes in the critical temperature of Hg120, which increases with pressure.; For the temperature and pressure studies of oligo(para-phenylene) materials, we performed a temperature study of hexaphenyl (6p) at p = 1bar and pressure study at 300K, We also performed pressure studies of 3p, 4p and 6p at 10K. We found that both an increase in temperature (10 to 300K) and an increase in pressure will planarize the phenyl rings in these molecular. Libration of the phenyl rings can be tracted via the intensities of the in-plane and C-C ring stretch modes. A W-type potential describes this libration, and our temperature studies provide activation energies associated with the libration. In our pressure studies we observe that there are existence two pressure ranges for all three samples both at 10K and 300K. This behavior clearly indicates that planarization will not complete at 300K at p = 1bar. However, pressure completes the planarization. The existence of two distinct pressure ranges in the frequency, linewidth and intensity of specific Raman modes clearly indicates the completion of the planarization of these materials. This is the first time such a discontinuity of pressure dependence of frequency, I ₁₂₀₈/I₁₂₂₀ have reported for these materials.