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Electron Tunneling in High Tc Superconductors

Published online by Cambridge University Press:  29 November 2013

J.M. Valles Jr.  and
R.C. Dynes
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Extract

Electron tunneling measurements have proven enormously valuable in studies of conventional superconductors. Very early measurements confirmed, in an especially convincing way, the existence of the superconducting energy gap, and more detailed studies demonstrated the spectral form of the gap and its temperature dependence. These measurements were instrumental in confirming in some detail the predictions of the Bardeen, Cooper, Schrieffer (BCS) theory of superconductivity in simple metals. For example, it was shown very clearly that the ratio of the energy gap (2Δ) and critical temperature Tc was close to the BCS value (2Δ/kTc = 3.5). As the sophistication of the technique improved, deviations from this BCS weak coupling limit became apparent (2Δ/kTc was measured to be >4 in materials like Pb, for example), and subtle structure in the current-voltage characteristics of tunnel junctions unearthed a signature of the electron-phonon interaction—the microscopic mechanism responsible for superconductivity in these traditional materials. Through a quantitative analysis of this structure, people were able to extract a function α2(ω)F(ω), which is the phonon density of states F(ω) modulated by the electron-phonon coupling function α2(ω). This function gave a quantitative description of the electron-phonon interaction and confirmed beyond a doubt that the electron-phonon interaction was responsible for superconductivity.

Type
Properties of High Tc Superconductors
Information
MRS Bulletin , Volume 15 , Issue 6 , June 1990 , pp. 44 - 49
Copyright
Copyright © Materials Research Society 1990

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References

1.Batlogg, B.et al., in Proc. International Conference on d and f Band Superconductors, edited by Buckel, W. and Werber, W. (Kernforschungszentrum Karlsruhe, Karlsruhe, Germany, 1982), p. 401–403.Google Scholar
2.Sleight, A.W., Gillson, J.L., and Bierstedt, P.E., Solid State Commun. 17 (1975) p. 27.CrossRefGoogle Scholar
3.Akimitsu, J., Ekino, T., and Kobayashi, K., Jpn. J. Appl. Phys. Suppl. 26 (1987) p. 995.CrossRefGoogle Scholar
4.McMillan, W.L. and Rowell, J.M., in Superconductivity, edited by Parks, R.D. (Dekker, New York, 1969).Google Scholar
5.McMillan, W.L., Phys. Rev. 167 (1968) p. 331.CrossRefGoogle Scholar
6.Matheiss, L.F. and Hamann, D.R., Phys. Rev. B 28 (1983) p. 4227.CrossRefGoogle Scholar
7.Zasadzinski, J.F.et al., Physica C 158 (1989) p. 519; and J.F. Zasadzinski et al., in Proc. Conference on Materials and Mechanisms of Superconductivity (Stanford, CA, 1989).CrossRefGoogle Scholar
8.Sato, H.et al., in Proc. Conference on Materials and Mechanisms of Superconductivity (Stanford, CA, 1989).Google Scholar
9.Moreland, J.et al., Phys. Rev. B 35 (1987) p. 8856; H.F.C. Hoevers et al., Physica 152C (Amsterdam, 1988) p. 105; J.R. Kirtley et al., Phys. Rev. B 35 (1987) p. 8846.CrossRefGoogle Scholar
10.Geerk, J., Xi, X.X., and Linker, G., “Conference on Materials and Mechanisms of Superconductivity,” Z. Phys. B 73 (Stanford, CA, 1989).Google Scholar
11.Cucolo, A.M.et al., Physics C 161 (1989) p. 351.Google Scholar
12.Fournel, A.et al., Europhys. Lett. 6 (1988) p. 653.CrossRefGoogle Scholar
13.Gurvitch, M.et al., Phys. Rev. Lett. 63 (1989) p. 1008; J.M. Valles Jr. et. al., in High-Temperature Superconductors: Fundamental Properties and Novel Materials Processing (Mater. Res. Soc. Symp. Proc. 169, Pittsburgh, PA, 1989), to be published.CrossRefGoogle Scholar
14.Lee, M., Kapitulnik, A., and Beasley, M.R., in Mechanisms of Temperature Superconductivity, edited by Kamimura, H. and Oshiyama, A. (Springer Series in Materials Science 11, Springer- Verlag, Heidelberg, 1989) p. 220; J.S. Tsai et al., in Mechanisms of Temperature Superconductivity, edited by H. Kamimura and A. Oshiyama (Springer Series in Materials Science 11, Springer- Verlag, Heidelberg, 1989), p. 229.CrossRefGoogle Scholar
15.Rowell, J.M., McMillan, W.L., and Feldmann, W.L., Phys. Rev. 180 (1969) p. 658.CrossRefGoogle Scholar
16.Takeuchi, I.et al., Physica 158C (Amsterdam, 1989) p. 83; J.S. Tasi and 1. Takeuchi in Strong Correlation and Superconductivity, edited by H. Fukuyama, S. Maekawa, and A.P. Malozemoff (Springer Series in SolidState Sciences, 89, Springer-Verlag, Berlin, Heidelberg, 1989) p. 98. These workers also suggest that their tunneling measurements on oriented thin films of YBCO show effects due to gap anisotropy.Google Scholar
17.Dynes, R.C. (unpublished).Google Scholar
18.Lyons, K.B.et al., Phys. Rev. Lett. 60 (1988) p. 732.CrossRefGoogle Scholar
19.Maki, K., in Superconductivity, edited by Parks, R.D., (Dekker, New York, 1969).Google Scholar
20.Edelstein, A.S., Phys. Rev. 180 (1968) p. 505.CrossRefGoogle Scholar
21.Dynes, R.C. as reported in Anderson, P.W. and Zou, Z., Phys. Rev. Lett. 60 (1988) p. 132.Google Scholar
22.Imry, Y. and Ovadyahu, Z., Phys. Rev. Lett. 49 (1982) p. 841; A.E. White, R.C. Dynes, and J.P. Garno, Phys. Rev. B 31 (1985) p. 1174.CrossRefGoogle Scholar
23.McMillan, W.L. and Mochel, J.M., Phys. Rev. 46 (1981) p. 556; R.C. Dynes and J.P. Garno, Phys. Rev. Lett. 46 (1981) p. 137.Google Scholar
24.Kirtley, J.R., Int. J. Mod. Phys. B., Feb. 1, 1990.Google Scholar
25.Batlogg, B.et al., Phys. Rev. Lett. 61 (1988) p. 1670.CrossRefGoogle Scholar
26.Anderson, P.W. and Zou, Z., Phys. Rev. Lett. 60 (1988) p. 132.CrossRefGoogle Scholar
27.Varma, C.M.et al., Phys. Rev. Lett. 63 (1989) p. 1996.CrossRefGoogle Scholar
28. See for example, Huang, Q.et al., Physica C 161 (1989) p. 141.CrossRefGoogle Scholar