Electron Tunneling into Superconducting Bismuth-Copper Oxide Systems
The energy gaps of the polycrystal1ine Bi-Sr-Ca-Cu-O and Bi-Sr-Cu-O superconductors have been measured by means of the point-contact tunneling technique. We find that the energy gaps at T=OK are 2Δ=76-81meV in Bi2Sr2Ca1Cu2Oy(Tc=76K), 91–100meV in Bi2Sr2Ca2Cu3Oy(Tc=105K) and 3.0–3.5meV in Bi2Sr2Cu1Oy (Tc=6.5K). Temperature variations of these energy gaps are also extracted. The ratios 2Δ/kTc are 11.6–12.4 for Bi2Sr2Ca1Cu2Oy, 10.0–11.0 for Bi2Sr2Ca2Cu3Oy, extremely larger than BCS value. 2Δ/kTc of Bi2Sr2Cu1Oy is 5.4–6.2, larger than those of the usual strong coupling superconductors. These results give the information about the difference of the pairing nature on the superconducting state between these materials which have multiple Cu02 layers or a single CuO2 layer between the SrO layers.
KeywordsSuperconducting State Electron Tunneling High Bias Region Cu02 Layer Copper Oxide System
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