Penetration depth study of very thin superconducting Nb films

Thomas R. Lemberger; Iulian Hetel; Jacob W. Knepper; F. Y. Yang

doi:10.1103/PhysRevB.76.094515

← Back to search

Penetration depth study of very thin superconducting Nb films

Thomas R. Lemberger, Iulian Hetel, Jacob W. Knepper, F. Y. Yang

DOI 10.1103/PhysRevB.76.094515 · Physical Review B

T1

Active bibliographic source — not scientific approval

Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.

Abstract

Using a low-frequency two-coil technique, we measure the magnetic penetration depth λ(T) of superconducting Nb films with thicknesses 20Å⩽d⩽228Å sputtered onto oxidized Si substrates. We find a phenomenological dependence of Tc on d, Tc∕8.5K≈tanh(d∕70Å) for films thinner than 250Å. λ−2(T)∕λ−2(0) is well fitted by weak-coupling dirty-limit theory with a weak-coupling gap, Δ(0)=1.8kBTc. λ−2(0) agrees with dirty-limit theory, given the experimental values of transition temperature Tc and residual resistivity ρ0. These results indicate that the suppression of Tc is due to mechanisms that weaken the effective pairing interaction and not due to pair breaking interactions.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.14	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.57	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.9	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.5	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6.8	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.7	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.17	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.45	Pressure not reported	midpoint
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	9.288	Pressure not reported	unknown