Angle-resolved phase-sensitive determination of the in-plane gap symmetry in YBa2Cu3O7−δ

  • An Erratum to this article was published on 01 May 2006


Understanding the nature of the ground state and its low-lying excitations in the copper oxide superconductors is a prerequisite for determining the origin of high-temperature superconductivity. A superconducting order parameter (that is, the energy gap) with a predominantly d X 2 Y 2 symmetry is well-established. However, various deviations from a pure d-wave pair state, such as the possibility of Cooper pairing with broken time-reversal symmetry or an admixed d X 2 Y 2 +s pair state, have been theoretically predicted and actively sought in numerous experimental studies. Here, we present an angle-resolved phase-sensitive technique for accurately determining the in-plane pairing symmetry, and demonstrate this technique in optimally doped YBa2Cu3O7−δ. We find that the gap along the b-axis (Cu–O chain) direction is at least 20% larger than that along the a-axis direction, and that any imaginary i dx y, is or ip component must be smaller than a few per cent of the d X 2 Y 2 component of the gap.

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Figure 1: Experimental ring geometry.
Figure 2: Schematic and SQUID microscope images of the rings of sample 1.
Figure 3: Integrated flux through the rings of sample 1, as a function of θ, the angle of the second junction normal relative to the majority twin a-axis direction.
Figure 4: SQUID images of sample 2.
Figure 5: Integrated flux through the rings of sample 2, as a function of θ, the second junction normal angle relative to the majority twin a-axis direction.


  1. 1

    van Harlingen, D. J. Phase-sensitive tests of the symmetry of the pairing state in the high-temperature superconductors-evidence for d x 2 − y 2 symmetry. Rev. Mod. Phys. 67, 515–535 (1995).

  2. 2

    Tsuei, C. C. & Kirtley, J. R. Pairing symmetry in cuprate superconductors. Rev. Mod. Phys. 72, 969–1016 (2000).

  3. 3

    Tsuei, C. C. & Kirtley, J. R. Phase-sensitive evidence for d-wave pairing symmetry in electron-doped cuprate superconductors. Phys. Rev. Lett. 85, 182–185 (2000).

  4. 4

    Tsuei, C. C. et al. Robust d x 2 − y 2 pairing symmetry in high-temperature superconductors. Phys. Rev. Lett. 93, 187004 (2004).

  5. 5

    Laughlin, R. B. The relationship between high-temperature superconductivity and the fractional quantum hall effect. Science 242, 525–533 (1988).

  6. 6

    Varma, C. M. Pseudogap phase and the quantum-critical point in copper-oxide metals. Phys. Rev. Lett. 83, 3538–3541 (1999).

  7. 7

    Sigrist, M. Time-reversal symmetry breaking states in high-temperature superconductors. Prog. Theor. Phys. 99, 899–929 (1998).

  8. 8

    Löfwander, T., Shumeiko, V. S. & Wendin, G. Andreev bound states in high-Tc superconducting junctions. Supercond. Sci. Technol. 14, R53–R77 (2001).

  9. 9

    Spielman, S. et al. Measurement of the spontaneous polar Kerr effect in YBa2Cu3O7 and Bi2Sr2CaCu2O8 . Phys. Rev. Lett. 68, 3472–3475 (1992).

  10. 10

    Lawrence, T. W., Szöker, A. & Laughlin, R. B. Absence of circular dichroism in high-temperature superconductors. Phys. Rev. Lett. 69, 1439–1442 (1992).

  11. 11

    Kaminski, A. et al. Spontaneous breaking of time reversal symmetry in the pseudogap state of a high-Tc superconductor. Nature 416, 610–613 (2002).

  12. 12

    Simon, M. E. & Varma, C. M. Detection and implications of a time-reversal breaking state in underdoped cuprates. Phys. Rev. Lett. 89, 247003 (2002).

  13. 13

    Fauqué, B. et al. Magnetic order in the pseudogap phase of high-Tc superconductors. Preprint at <> 2005.

  14. 14

    Covington, M. et al. Observation of surface-induced broken time-reversal symmetry in YBa2Cu3O7 tunnel junctions. Phys. Rev. Lett. 79, 277–280 (1997).

  15. 15

    Dagan, Y. & Deutscher, G. Doping and magnetic field dependence of in-plane tunneling into YBa2Cu3O7−x: possible evidence for the existence of a quantum critical point. Phys. Rev. Lett. 87, 177004 (2001).

  16. 16

    Sharoni, A. et al. Local and macroscopic tunneling spectroscopy of Y1−xCaxBa2Cu3O7−δ films: evidence for a doping-dependentis orid xy component in the order parameter. Phys. Rev. B 65, 134526 (2002).

  17. 17

    Mathai, A., Gim, Y., Black, R. C., Amar, A. & Wellstood, F. C. Experimental proof of a time-reversal-invariant order parameter with a π shift in YBa2Cu3O7−δ . Phys. Rev. Lett. 74, 4523–4526 (1995).

  18. 18

    Schulz, R. R. et al. Design and realization of an all d-wave dc π-superconducting quantum interference device. Appl. Phys. Lett. 76, 912–914 (2002).

  19. 19

    Beasley, M. R., Lew, D. & Laughlin, R. B. Time-reversal symmetry breaking in superconductors: a proposed experimental test. Phys. Rev. B 49, 12330–12332 (1994).

  20. 20

    Ng, T.-K. & Varma, C. M. Experimental signatures of time-reversal-violating superconductors. Phys. Rev. B 70, 054514 (2004).

  21. 21

    Polturak, E., Koren, G., Cohen, D. & Aharoni, E. Measurements of the anisotropy and temperature dependence of the in-plane energy gap in YBa2Cu3O7−δ using Andreev reflections. Phys. Rev. B 47, 5270–5274 (1993).

  22. 22

    Basov, D. N. et al. In-plane anisotropy of the penetration depth in YBa2Cu3O7−x and YBa2Cu4O8 superconductors. Phys. Rev. Lett. 74, 598–601 (1995).

  23. 23

    Limonov, M. F., Rykov, A. I. & Tajima, S. Raman scattering study on fully oxygenated YBa2Cu3O7 single crystals:xy anisotropy in the superconductivity-induced effects. Phys. Rev. Lett. 80, 825–828 (1998).

  24. 24

    Lu, D. H. et al. Superconducting gap and strong in-plane anisotropy in untwinned YBa2Cu3O7−δ . Phys. Rev. Lett. 86, 4370–4373 (2001).

  25. 25

    Engelhardt, A., Dittmann, R. & Braginski, A. I. Subgap conductance features of YBa2Cu3O7−δ edge Josephson junctions. Phys. Rev. B 59, 3815–3822 (1999).

  26. 26

    Smilde, H. J. H. et al. Admixtures to d-wave gap symmetry in untwinned YBa2Cu3O7 superconducting films measured by angle-resolved electron tunneling. Phys. Rev. Lett. 95, 257001 (2005).

  27. 27

    Orenstein, J. & Millis, A. J. Advance in the physics of high-temperature superconductivity. Science 288, 468–474 (2000).

  28. 28

    Gim, Y., Mathai, A., Black, R., Amar, A. & Wellstood, F. C. Angular dependence of the symmetry of the order parameter in YBa2Cu3O7−δ . IEEE Trans. Appl. Supercond. 7, 2331–2334 (1997).

  29. 29

    van Harlingen, D. J., Hilliard, J. E., Plourde, B. L. T. & Yanoff, B. D. Extending SQUID interferometry beyond the cuprates and beyond d-wave symmetry. Physica C 317–318, 410–420 (1999).

  30. 30

    Clem, J. R. American Physical Society, Annual March Meeting, 1998, Abstract K36.06 (American Physical Society, College Park, Maryland, 1998).

  31. 31

    Smilde, H. J. H., Hilgenkamp, H., Rijnders, G., Rogalla, H. & Blank, D. H. A. Enhanced transparency ramp-type Josephson contacts through interlayer deposition. Appl. Phys. Lett. 80, 4579–4581 (2002).

  32. 32

    Dekkers, J. M. et al. Monocrystalline YBa2Cu3O7−x thin films on vicinal SrTiO3 (001) substrates. Appl. Phys. Lett. 83, 5199–5201 (2003).

  33. 33

    Kirtley, J. R. et al. High-resolution integrated scanning SQUID microscope. Appl. Phys. Lett. 66, 1138–1140 (1995).

  34. 34

    Sigrist, M. & Rice, T. M. Paramagnetic effect in high-T c superconductors-a hint for d-wave superconductivity. J. Phys. Soc. Jpn 61, 4283–4286 (1992).

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We would like to thank D. Blank, A. Brinkman, M. Dekkers, A. Golubov, R. Koch, D. Newns, G. Rijnders, F. Roesthuis, H. Rogalla, H.-J. Smilde and C. Varma for discussions. This work was supported by the Dutch Foundation for Research on Matter (FOM), the Netherlands Organization for Scientific Research (NWO), the Dutch STW NanoNed programme, the European Science Foundation (ESF) PiShift programme, and by the Center for Probing the Nanoscale (CPN), an NSF NSEC, NSF Grant No. PHY-0425897.

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Kirtley, J., Tsuei, C., Ariando et al. Angle-resolved phase-sensitive determination of the in-plane gap symmetry in YBa2Cu3O7−δ. Nature Phys 2, 190–194 (2006).

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