Phonon, plasmon and gap behavior in superconducting high-Tc Y1Ba2Cu3O7 and Gd1.5Ba1.5Cu3O7☆

Abstract Infrared and Raman spectra (50 – 600 cm -1 of superconducting Y 1 Ba 2 Cu 3 O 7 and Gd 1.5 Ba 1.5 Cu 3 O 7 (T c (onset) = 91 − 95K) show strong phonon modes nearly independent of the rare earth (at 93–100, 158, 198–201, 270–275 and 298–311 cm -1 ) and low plasma frequencies ( ω p = 450 − 1220 cm -1 ; 0.06 − 0.15 eV). Data below T c are fitted in detail with 2Δ kT c = 3.6 ± 0.2 using a minority of superconducting carriers. Temperature-dependent longitudinal plasmon-phonon modes at 233 cm -1 (near the gap) and at 140–155 cm -1 may be associated with plasmon-mediated superconducting processes.