Journal of Low Temperature Physics

, Volume 179, Issue 1–2, pp 108–112 | Cite as

Observation of a Bulk Nodal-Gap in Overdoped Y\(_{0.9}\)Ca\(_{0.1}\)Ba\(_{2}\)Cu\(_{3}\)O\(_{7-\delta }\) Thin Films

  • N. BacharEmail author
  • Y. Bechor
  • B. Gorshunov
  • E. Farber


Complex conductivity of overdoped Y\(_{0.9}\)Ca\(_{0.1}\)Ba\(_{2}\)Cu\(_{3}\)O\(_{7-\delta }\) thin films was measured in Terahertz frequency using frequency and time domain methods. The films were measured in the frequency range of 3–100 cm\(^{-1}\) and in the temperature range of 20–300 K. Results show a possible deviation from a pure \(d_{x^{2}-y^{2}}\)-wave superconductor, indicated by the existence of an energy sub-gap in overdoped Y\(_{0.9}\)Ca\(_{0.1}\)Ba\(_{2}\)Cu\(_{3}\)O\(_{7-\delta }\) films. Evidence for this sub-gap appears as non-monotonic behavior of \(\sigma _{1}(\omega ,T)\) as a function of frequency followed by a sharp decrease at low frequencies, and a dip in the imaginary part of the optical conductivity multiplied by frequency, \(\omega {{\sigma }_{2}}(\omega ,T)\). The mentioned features were observed at energy of about 1.2 meV in 10 % Ca-doped YBCO thin films. Our complex conductivity spectra are in agreement with the theoretical prediction obtained by using a mixed symmetry order parameter within the Born limit, shown by Schürrer et al. We suggest that these observations are direct evidence for a nodal gap obtained in a \(d_{x^{2}-y^{2}}\)-wave superconductor and can be theoretically clarified by adding an imaginary component as \(is\) or \(i{{d}_{xy}}\) to the main \(d_{x^{2}-y^{2}}\)-wave order parameter.


YBCO Pairing Symmetry THz spectroscopy 


  1. 1.
    G. Deutscher, Rev. Mod. Phys. 77, 109 (2005)CrossRefADSGoogle Scholar
  2. 2.
    M. Fogelström, D. Rainer, J.A. Sauls, Phys. Rev. Lett. 74, 3451 (1995)CrossRefGoogle Scholar
  3. 3.
    Y. Dagan, G. Deutscher, Eur. Phys. Lett. 57, 4444 (2002)CrossRefGoogle Scholar
  4. 4.
    D. Pines, Physica C 235–240, 113 (1994)CrossRefGoogle Scholar
  5. 5.
    D. Pines, P. Monthoux, J. Phys. Chem. Solids 56, 1651 (1995)CrossRefADSGoogle Scholar
  6. 6.
    P.W. Anderson, Science 235, 1196 (1987)CrossRefADSGoogle Scholar
  7. 7.
    P.W. Anderson, Physica C 153, 527 (1988)CrossRefADSGoogle Scholar
  8. 8.
    S. Sachdev, Physica A 313, 252–283 (2002)CrossRefADSGoogle Scholar
  9. 9.
    G. Sangiovanni, M. Capone, S. Caparara, C. Castellani, C. Di Castro, M. Grilli (2001). arXiv:Cond-mat/o111107
  10. 10.
    J. Friedel, M. Kohmoto, Int. J. Mod. Phys. B 15, 51 (2001)CrossRefGoogle Scholar
  11. 11.
    Y. Dagan, R. Krupke, G. Deutscher, Phys. Rev. B 62, 146 (2000)CrossRefADSGoogle Scholar
  12. 12.
    C. Tsuei, J. Kirtley, Physica C: Supercond. 341, 1625 (2000)CrossRefADSGoogle Scholar
  13. 13.
    F. Wenger, S. Östlund, Phys. Rev. B 47, 5977 (1993)CrossRefADSGoogle Scholar
  14. 14.
    R. Krupke, G. Deutscher, Phys. Rev. Lett. 83, 4634 (1999)CrossRefADSGoogle Scholar
  15. 15.
    A. Sharoni, O. Millo, A. Kohen, Y. Dagan, R. Beck, G. Deutscher, G. Koren, Phys. Rev. B 65, 1 (2002)CrossRefGoogle Scholar
  16. 16.
    Y. Dagan, R. Krupke, G. Deutscher, Eur. Phys. Lett. 51, 116 (2000)CrossRefADSGoogle Scholar
  17. 17.
    E. Farber, G. Deutscher, B.P. Gorshunov, M. Dressel, Europhys. Lett. 67, 834 (2004)CrossRefADSGoogle Scholar
  18. 18.
    E. Farber, G. Deutscher, J. Low Temp. Phys. 131, 563 (2003)CrossRefADSGoogle Scholar
  19. 19.
    D.N. Basov, T. Timusk, Rev. Mod. Phys. 77, 721 (2005)CrossRefADSGoogle Scholar
  20. 20.
    I. Schürrer, E. Schachinger, J.P. Carbotte, Physica C: Supercond. 303, 287 (1998)CrossRefADSGoogle Scholar
  21. 21.
    R. Krupke, M. Azoulay, G. Deutscher, in Second-Generation HTS Conductors, A. Goyal, (ed.). Kluwer Academic Publishers, Philip Drive Norwell, MA (2000).Google Scholar
  22. 22.
    C.A. Schmuttenmaer, Chem. Rev. 104, 1759 (2004)CrossRefGoogle Scholar
  23. 23.
    D. Grischkowsky, S. Keiding, M. van Exter, C. Fattinger, J. Opt. Soc. Am. B 7, 2006 (2006)CrossRefADSGoogle Scholar
  24. 24.
    B.P. Gorshunov, A.A. Volkov, I. Spektor, A. Prokhorov, A. Mukhin, M. Dressel, S. Uchida, A. Loidl, Int. J. Infrared Millimeter Waves 26, 1217 (2005)CrossRefADSGoogle Scholar
  25. 25.
    A.V. Pronin, M. Dressel, A. Pimenov, A. Loidl, I.V. Roshchin, L.H. Greene, Phys. Rev. B 57, 416 (1998)CrossRefGoogle Scholar
  26. 26.
    M.V. Abrashev, A.P. Litvinchuk, M.N. Iliev, R.L. Meng, V.N. Popov, V.G. Ivanov, R.A. Chakalov, C. Thomsen, Phys. Rev. B 59, 4146 (1999)CrossRefADSGoogle Scholar
  27. 27.
    A. Berlinsky, C. Kallin, G. Rose, A.C. Shi, Phys. Rev. B 48, 4074 (1993)CrossRefADSGoogle Scholar
  28. 28.
    A.B. Kuzmenko, Rev. Sci. Instrum. 76, 083108 (2005)CrossRefADSGoogle Scholar
  29. 29.
    E. Farber, G. Deutscher, J.P. Contour, E. Jerby, Eur. Phys. J. B 5, 159 (1998)CrossRefADSGoogle Scholar

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© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Laboratory for Superconductivity and Optical SpectroscopyAriel UniversityArielIsrael
  2. 2.Prokhorov Institute of General PhysicsRussian Academy of SciencesMoscowRussia

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