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Thin Film Tunneling in Superconductor. Lu Lu and Xu Luo Physics Department, Brown University Lu_lu@brown.edu. Introduction.
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Thin Film Tunneling in Superconductor Lu Lu and XuLuo Physics Department, Brown University Lu_lu@brown.edu
Introduction • The modern theory of superconductivity, known as the BCS theory has found its most outstanding success in the prediction of temperature-dependent energy gap of superconductors below the transition temperature Tc.
Original Experiment Al-Al2O3-Pb sandwich Indium Contacts; Aluminum(Al); Alumina (Al2O3) Lead(Pb) Current-voltage characteristics of an Al-Al2O3-Pb sandwich at various temperatures. IvarGiaever, Study of Superconductor by Electron Tunneling. Phys. Rev.Vol 122, Num 4. January 3, 1961
Theory • Fermi Level For a system of identical fermions, the average number of fermions in a single-particle state i, is given by the Fermi–Dirac (F–D) distribution: Energy dependence
Preparation of Thin Film Chromium Aluminum Alumina Lead Evaporator System
Measurement Set-up Low temperature cryostat Electronic circuit for measuring the thin film tunneling
Energy Gap of Lead (Pb) ◆The experimental result of half energy gap is around (1.34 +/- 0.05) X 10^(-3) eV, similar to the theoretical value. ◆The second graph shows that energy gap decreases with lower temperature.