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Title: Determination of the optical properties of La 2-xBa xCuO₄ for several dopings, including the anomalous x=1/8 phase

The optical properties of single crystals of the high-temperature superconductor La 2-xBa xCuO₄ have been measured over a wide frequency and temperature range for light polarized in the a-b planes and along the c axis. Three different Ba concentrations have been examined, x=0.095 with a critical temperature T c=32 K, x=0.125 where the superconductivity is dramatically weakened with T c≅2.4 K, and x=0.145 with T c≅24 K. The in-plane behavior of the optical conductivity for these materials at high temperature is described by a Drude-like response with a scattering rate that decreases with temperature. Below T c in the x=0.095 and 0.145 materials there is a clear signature of the formation of a superconducting state in the optical properties allowing the superfluid density (ρ s0) and the penetration depth to be determined. In the anomalous 1/8 phase, some spectral weight shifts from lower to higher frequency (≳300 cm⁻¹) on cooling below the spin-ordering temperature T so≅42 K, associated with the onset of spin-stripe order; we discuss alternative interpretations in terms of a conventional density-wave gap versus the response to pair-density-wave superconductivity. The two dopings for which a superconducting response is observed both fall on the universal scaling line ρ s0/8≅4.4σmore » dcT c, which is consistent with the observation of strong dissipation within the a-b planes. The optical properties for light polarized along the c axis reveal an insulating character dominated by lattice vibrations, superimposed on a weak electronic background. No Josephson plasma edge is observed in the low-frequency reflectance along the c axis for x=1/8; however, sharp plasma edges are observed for x=0.095 and 0.145 below T c.« less
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Publication Date:
Publisher's Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 85; Journal Issue: 13; Related Information: CHORUS Timestamp: 2017-06-20 13:07:46; Journal ID: ISSN 1098-0121
American Physical Society
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier: