Optical absorptivity of La1.87Sr0.13CuO4 below the superconducting plasma edge

J. T. Birmingham; S. M. Grannan; P. L. Richards; J. Kircher; M. Cardona; A. Wittlin

doi:10.1103/PhysRevB.59.647

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Optical absorptivity of La1.87Sr0.13CuO4 below the superconducting plasma edge

J. T. Birmingham, S. M. Grannan, P. L. Richards, J. Kircher, M. Cardona, A. Wittlin

DOI 10.1103/PhysRevB.59.647 · Physical Review B

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Abstract

We have directly measured the far-infrared absorptivity of single crystal La1.87Sr0.13CuO4 at 2 K for radiation between 6 and 420 cm−1 polarized along the c axis. We have computed the dielectric functions ɛc(ω) and conductivity σc(ω) using a Kramers-Kronig analysis. The existence of nonzero losses below the plasma edge and down to the lowest frequency measured is consistent with a model of a superconducting gap with nodes. From the calculation of ɛc(ω), we deduce a value of 230±10cm−1 for the unscreened plasma frequency in the superconducting state. A small peak in the σ1c(ω) is seen near 10 cm−1.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
La1.87Sr0.13CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	31	Pressure not reported	unknown
La1.87Sr0.13CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	31	Pressure not reported	unknown
La1.85Sr0.15CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown