INFRARED REFLECTION OF EPITAXIAL TL2BA2CACU2O8 THIN-FILMS IN THE NORMAL AND SUPERCONDUCTING STATES

For T>Tc, the frequency-dependent conductivity, σ(ω), is Drude-like in the far-infrared (IR) and indicates a broad absorption in the mid-IR. For T<Tc, RS(ω)=1.0±0.005 for ω<200 cm-1. All the normal state Drude oscillator strength shifts to δ(ω), but with no shift or loss of oscillator strength from the mid-IR. No feature in R(ω) or σ(ω) can be assigned to the energy gap. The penetration depth (λL) and carrier density in the condensate (NS) are λL≈2000Å and NS≈4.5X1020(m*/m) cm-3 (m* and m are the optical effective mass and free-electron mass). The data demonstrate that the quality of these epitaxial Tl2Ba2CaCu2O8 films is comparable to the best YBa2Cu3O7-δ films. © 1990.