Energy Gap Measurement Made on Cryogenically Cleaved Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O Surfaces
The surfaces of the cryogenically cleaved Y-Ba-Cu-O film and Bi-Sr-Ca-Cu-O films are studied. Energy gaps are measured at these cleaved surfaces by the tunneling technique. (001), (103) and (110) oriented Y-Ba-Cu-O epitaxial films are broken in a cryogenic environment along the appropriate directions together with the SrTiO3 substrate. Pb electrode is brought close to the in situ clean broken film edge. The normalized energy gap 2Δ(0)/kBTc measured in the direction along and perpendicular to the Cu-O plane are found to be 6.0±0.2 and 3.6±0.2 respectively. These values are independent of the variation in the values of Tc within the examined range of 40K∼90K. The gap difference structure at ΔYBCO-Δpb is observed which helps identifying the value of energy gap of the oxide superconductor unambiguously. (001) oriented epitaxial Bi-Sr-Ca-Cu-O films are also studied. The gap voltage along ab-plane is near 20 mV, but the gap opening temperature of Bi-Sr-Ca-Cu-O junction is not identified in the experiment.
KeywordsTunnel Junction Oxide Superconductor Film Edge Josephson Frequency Junction Impedance
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