Optical determination of the superconducting energy gap in electron-doped Pr1.85Ce0.15CuO4

Abstract

The optical properties of single crystal Pr1.85Ce0.15CuO4 have been measured over a wide frequency range above and below the critical temperature (Tc≃20K). In the normal state the coherent part of the conductivity is described by the Drude model, from which the scattering rate just above Tc is determined to be 1∕τ≃80cm−1. The condition that ℏ∕τ≈2kBT near Tc appears to be a general result in many of the cuprate superconductors. Below Tc the formation of a superconducting energy gap is clearly visible in the reflectance, from which the gap maximum is estimated to be Δ0≃35cm−1 (4.3meV). The ability to observe the superconducting energy gap in the optical properties favors the nonmonotonic over the monotonic description of the d-wave gap. The penetration depth for T⪡Tc is λ≃2000Å, which when taken with the estimated value for the dc conductivity just above Tc of σdc≃35×103Ω−1cm−1 places this material on the general scaling line for the cuprates defined by 1∕λ2∝σdc(T≃Tc)∙Tc. These results are consistent with the observation that 1∕τ≈2Δ0, which implies that the material is not in the clean limit.

Source-reported materials — not catalogue approval

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