Infrared studies of the normal and superconducting states of Y1Ba2Cu3O7
by R. T. Collins, Z. Schlesinger, F. H. Holtzberg, P. Chaudhari, C. A. Feild
We describe infrared measurements of the a–b-plane response of Y1Ba2Cu3O7 crystals with Tc ≃ 92 K. We observe a self-energy structure at a characteristic energy of 500 cm−1 (8kTc), the appearance of which coincides with the transition to the superconducting state. The nature of this self-energy anomaly is consistent with its identification as a nodeless a–b-plane energy gap at 2Δ ≃ 8kTc. On the basis of temperature-dependent measurements above Tc, we suggest that the normal state can be primarily characterized by a carrier band with an enhanced low-frequency mass and a frequency-dependent scattering rate. Our data indicate that these arise from coupling to an excitation spectrum with characteristic frequencies up to ωc ~ 700 cm−1 and a coupling strength of λ ≃ 2–3.
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