首页> 美国政府科技报告 >Probing Thin-Film YBa2Cu307-Delta Superconductors by Second Harmonic Generation Using Femtosecond Laser Pulses.
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Probing Thin-Film YBa2Cu307-Delta Superconductors by Second Harmonic Generation Using Femtosecond Laser Pulses.

机译:利用飞秒激光脉冲二次谐波探测薄膜YBa2Cu307-Delta超导体。

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摘要

High temperature superconducting thin films of YBa2Cu307-Delta are examined by measuring the second-harmonic-generated (SHG) signal from an incident 60 fs laser pulse of 2.0 eV (620 nm) in air at room temperature. As oxygen stoichiometry is varied ( 0. 00 < Delta < 0. 50 ), large changes in the SHG intensity are observed. The oxygen content of the films is independently determined by measuring i) the c-axis lattice parameter derived from x-ray diffraction and ii) the stoichiometry of the films determined by elastic backscattering spectrometry. We report a negative correlation of the SHG intensity with the c-axis parameter indicating that a known compression of the c-axis leads to a larger SHG signal. An additional experiment in which the SHG intensity is monitored as a function of temperature (300 K to 20 K) in vacuum is performed. A gradual increase of - 50 % in the SHG intensity is observed as the temperature is lowered which can also be correlated to a decrease in the length of the c-axis. Other experiments including rotation anisotropy and polarization of the incident and analyzer beams are also discussed. Ultrafast Phenomena, Thin films, Second harmonic generation, superconductors.

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