We have measured the tunneling characteristics (I, dV/dI, and d 2V/dI2 vs. voltage) for a series of junctions of the form Al-oxide-Zn-Pb for Zn thicknesses ranging from 400 to 4000 Å (T > T c,Zn). From the first and second derivative characteristics we observe two electron interference effects (Tomasch and McMillan interference) plus structure due to the interaction of the superconducting electrons and the Zn phonons. For junctions with Zn layer thicknesses ≲800 Å these contributions can be separated by application of a magnetic field less than the critical field H c of the sandwich. For thicker sandwiches a breakdown occurs before H c is reached. The dominant zero-field interference effect is seen to be the Tomasch oscillation. The electron interference terms provide a direct measurement of the Fermi velocity in Zn, while interactions with the Zn phonon provide a measurement of the electron-phonon coupling constant. For Zn we find V f = 0.73 ± 0.1 × 108 cm/sec and λ (dimensionless electron-phonon coupling constant) = 1.38 ± 0.1. Measurement of the dependence of the breakdown field on the Zn layer thickness indicate that proximity effect Zn exhibits a zero-field penetration depth of 750 Å.
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References
G. Deutscher and P. G. de Gennes, in Superconductivity, R. Parks, ed. (Marcel Dekker, New York, 1969), p. 1005.
P. Nédellec, Ann. Phys. 2, 253 (1977).
A. Gilabert, Ann. Phys. 2, 203 (1977).
W. L. McMillan and J. M. Rowell, in Superconductivity, R. Parks, ed. (Marcel Dekker, New York, 1969), p. 561.
A. F. Andreev, Zh. Eksp. Teor. Fiz. 46, 1823 (1964). [Sov. Phys.—JETP 19, 1228 (1964)].
J. M. Rowell and W. L. McMillan, Phys. Rev. Lett. 16, 453 (1966).
P. Nédellec, Thesis, University of Paris (1975), unpublished.
J. M. Rowell, Phys. Rev. Lett. 30, 167 (1973).
G. B. Arnold, Phys. Rev. B 17, 3576 (1978).
G. B. Arnold, Theory of Thin Proximity Effect Sandwiches (to be published).
E. L. Wolf, Solid State Phys. 30, 1 (1975).
P. M. Chaikin, and P. K. Hansma, Phys. Rev. Lett. 36, 1552 (1976).
P. M. Chaikin, G. Arnold, and P. K. Hansma, J. Low Temp. Phys. 26, 229 (1977).
P. M. Chaikin, B. F. Donovan-Vojtovik, J. A. Wilson, and G. Deutscher, Solid State Comm. 21, 331 (1977).
Orsay Group on Superconductivity, in Quantum Fluids: Proc. of the 1965 Sussex University Symposium, D. Brewer, ed. (North-Holland, Amsterdam, 1966).
P. G. de Gennes and J. P. Hurault, Phys. Lett. 17, 181 (1965).
W. L. McMillan, Phys. Rev. 167, 331 (1968).
J. G. Adler, T. T. Chen, and J. Straus, Rev. Sci. Instr. 42, 362 (1971).
D. St. James, J. Phys. (Paris) 25, 899 (1964).
P. G. de Gennes and D. St. James, Phys. Lett. 4, 151 (1963).
W. J. Tomasch, in Tunneling Phenomena in Solids, E. Burstein and S. Lundquist, eds. (Plenum Press, New York, 1969), p. 315.
Orsay Group on Superconductivity, Phys. Kondens. Materie 6, 307 (1967).
J. P. Burger, G. Deutscher, E. Guyon, and A. Martinet, Phys. Lett. 17, 180 (1965).
G. Bose, B. B. Tripathi, and H. C. Gupta, J. Phys. Soc. Japan 34, 1006 (1973).
E. Bauer, in Single Crystal Films, M. H. Francombe and H. Sato, eds. (Macmillan, New York, 1964), p. 52.
J. M. Rowell, W. L. McMillan, and R. C. Dynes, A Tabulation of the Electron-Phonon Interaction in Superconducting Metals and Alloys, Part I, unpublished.
T. G. Worlton and R. E. Schmunk, Phys. Rev. B 3 (1971).
C. Kittel, Introduction to Solid State Physics (Wiley, New York, 1971), p. 219.
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Work supported under NSF Contract DMR 7812000.
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Wilson, J.A. Tunneling investigation of Zn-Pb proximity sandwiches. J Low Temp Phys 35, 135–146 (1979). https://doi.org/10.1007/BF00121725
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DOI: https://doi.org/10.1007/BF00121725