Penetration depth study of very thin superconducting Nb films

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2007-09-20

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American Physical Society

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Using a low-frequency two-coil technique, we measure the magnetic penetration depth λ(T) of superconducting Nb films with thicknesses 20 Å≤d≤228 Å sputtered onto oxidized Si substrates. We find a phenomenological dependence of T_c on d, T_c/8.5 K≈tanh(d/70 Å) for films thinner than 250 Å. λ^−2(T)/λ^−2(0) is well fitted by weak-coupling dirty-limit theory with a weak-coupling gap, Δ(0)=1.8k_BT_c. λ^−2(0) agrees with dirty-limit theory, given the experimental values of transition temperature T_c and residual resistivity ρ_0. These results indicate that the suppression of T_c is due to mechanisms that weaken the effective pairing interaction and not due to pair breaking interactions.

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Thomas R. Lemberger et al, "Penetration depth study of very thin superconducting Nb films," Physical Review B 76, no. 9 (2007), doi:10.1103/PhysRevB.76.094515

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http://hdl.handle.net/1811/48153

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Ohio State University Research and Scholarship