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Imaging the two gaps of the high-temperature superconductor Bi2Sr2CuO6+x

Nature Physics volume 3, pages 802–806 (2007)Cite this article

Abstract

The nature and behaviour of electronic states in high-temperature superconductors are the centre of much debate. The pseudogap state, observed above the superconducting transition temperature, Tc, is seen by some as a precursor to the superconducting state. Others view it as a competing phase. Recently, this discussion has focused on the number of energy gaps in the system. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here, we use temperature-dependent scanning tunnelling spectroscopy of (Bi1−yPby)2Sr2CuO6+x to clarify the situation. We find a previously unobserved narrow and homogeneous gap that vanishes near Tc, superimposed on the typically observed inhomogeneous and broad gap, which is only weakly temperature dependent. These results not only support the two-gap picture, but also explain previously troubling differences between scanning tunnelling microscopy and other experimental measurements.

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Figure 1: Spatially averaged spectral temperature dependence.
Figure 2: Inhomogeneity at low temperatures.
Figure 3: Temperature evolution of inhomogeneity.
Figure 4: Small-gap homogeneity.
Figure 5: Small-gap temperature dependence.

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References

  1. Fischer, Ø., Kugler, M., Maggio-Aprile, I., Berthod, C. & Renner, C. Scanning tunneling spectroscopy of high-temperature superconductors. Rev. Mod. Phys. 79, 353–419 (2007).

    Article  ADS  Google Scholar 

  2. Renner, C., Revaz, B., Genoud, J. Y., Kadowaki, K. & Fischer, Ø. Pseudogap precursor of the superconducting gap in under- and overdoped Bi2Sr2CaCu2O8+δ . Phys. Rev. Lett. 80, 149–152 (1998).

    Article  ADS  Google Scholar 

  3. Kugler, M., Fischer, Ø., Renner, C., Ono, S. & Ando, Y. Scanning tunneling spectroscopy of Bi2Sr2CuO6+δ: New evidence for the common origin of the pseudogap and superconductivity. Phys. Rev. Lett. 86, 4911–4914 (2001).

    Article  ADS  Google Scholar 

  4. Kondo, T. et al. Contribution of electronic structure to thermoelectric power in (Bi,Pb)2(Sr,La)2CuO6+δ . Phys. Rev. B 72, 024533 (2005).

    Article  ADS  Google Scholar 

  5. Anderson, P. W. The resonating valence bond state in La2CuO4 and superconductivity. Science 235, 1196–1198 (1987).

    Article  ADS  Google Scholar 

  6. Geshkenbein, V. B., Ioffe, L. B. & Larkin, A. I. Superconductivity in a system with preformed pairs. Phys. Rev. B 55, 3173–3180 (1997).

    Article  ADS  Google Scholar 

  7. Randeria, M., Trivedi, N., Moreo, A. & Scalettar, R. T. Pairing and spin gap in the normal state of short coherence length superconductors. Phys. Rev. Lett. 69, 2001–2004 (1992).

    Article  ADS  Google Scholar 

  8. Emery, V. J. & Kivelson, S. A. Importance of phase fluctuations in superconductors with small superfluid density. Nature 374, 434–437 (1995).

    Article  ADS  Google Scholar 

  9. Franz, M. & Millis, A. J. Phase fluctuations and spectral properties of underdoped cuprates. Phys. Rev. B 58, 14572–14580 (1998).

    Article  ADS  Google Scholar 

  10. Franz, M. & Tesanovic, Z. Algebraic Fermi liquid from phase fluctuations: “Topological” fermions, vortex “Berryons,” and QED3 theory of cuprate superconductors. Phys. Rev. Lett. 87, 257003 (2001).

    Article  ADS  Google Scholar 

  11. Anderson, P. W. et al. The physics behind high-temperature superconducting cuprates: The ‘plain vanilla’ version of RVB. J. Phys. Condens. Matter 16, R755–R769 (2004).

    Article  Google Scholar 

  12. Cren, T., Roditchev, D., Sacks, W. & Klein, J. Nanometer scale mapping of the density of states in an inhomogeneous superconductor. Europhys. Lett. 54, 84–90 (2001).

    Article  ADS  Google Scholar 

  13. Lang, K. M. et al. Imaging the granular structure of high-Tc superconductivity in underdoped Bi2Sr2CaCu2O8+δ . Nature 415, 412–416 (2002).

    Article  ADS  Google Scholar 

  14. Pan, S. H. et al. Microscopic electronic inhomogeneity in the high-Tc superconductor Bi2Sr2CaCu2O8+x . Nature 413, 282–285 (2001).

    Article  ADS  Google Scholar 

  15. Howald, C., Fournier, P. & Kapitulnik, A. Inherent inhomogeneities in tunneling spectra of Bi2Sr2CaCu2O8−x crystals in the superconducting state. Phys. Rev. B 64, 100504 (2001).

    Article  ADS  Google Scholar 

  16. McElroy, K. et al. Atomic-scale sources and mechanism of nanoscale electronic disorder in Bi2Sr2CaCu2O8+δ . Science 309, 1048–1052 (2005).

    Article  ADS  Google Scholar 

  17. Yazdani, A., Howald, C. M., Lutz, C. P., Kapitulnik, A. & Eigler, D. M. Impurity-induced bound excitations on the surface of Bi2Sr2CaCu2O8 . Phys. Rev. Lett. 83, 176–179 (1999).

    Article  ADS  Google Scholar 

  18. Hudson, E. W. et al. Interplay of magnetism and high-Tc superconductivity at individual Ni impurity atoms in Bi2Sr2CaCu2O8+δ . Nature 411, 920–924 (2001).

    Article  ADS  Google Scholar 

  19. Nunner, T. S., Andersen, B. M., Melikyan, A. & Hirschfeld, P. J. Dopant-modulated pair interaction in cuprate superconductors. Phys. Rev. Lett. 95, 177003 (2005).

    Article  ADS  Google Scholar 

  20. Deutscher, G. Coherence and single-particle excitations in the high-temperature superconductors. Nature 397, 410–412 (1999).

    Article  ADS  Google Scholar 

  21. Mourachkine, A. Andreev reflections and tunneling spectroscopy on underdoped Nd1.85Ce0.15CuO4−δ . Europhys. Lett. 50, 663–667 (2000).

    Article  ADS  Google Scholar 

  22. Wang, Y., Li, L. & Ong, N. P. Nernst effect in high-TC superconductors. Phys. Rev. B 73, 024510 (2006).

    Article  ADS  Google Scholar 

  23. Miyakawa, N. et al. Predominantly superconducting origin of large energy gaps in underdoped Bi2Sr2CaCu2O8+δ from tunneling spectroscopy. Phys. Rev. Lett. 83, 1018–1021 (1999).

    Article  ADS  Google Scholar 

  24. Loram, J. W., Tallon, J. L. & Liang, W. Y. Absence of gross static inhomogeneity in cuprate superconductors. Phys. Rev. B 69, 060502 (2004).

    Article  ADS  Google Scholar 

  25. Mashima, H. et al. Electronic inhomogeneity of heavily overdoped Bi2−xPbxSr2CuOy studied by low-temperature scanning tunneling microscopy/spectroscopy. Phys. Rev. B 73, 060502 (2006).

    Article  ADS  Google Scholar 

  26. Zheng, G.-q., Kuhns, P. L., Reyes, A. P., Liang, B. & Lin, C. T. Critical point and the nature of the pseudogap of single-layered copper-oxide Bi2Sr2−xLaxCuO6+δ superconductors. Phys. Rev. Lett. 94, 047006 (2005).

    Article  ADS  Google Scholar 

  27. McElroy, K. et al. Coincidence of checkerboard charge order and antinodal state decoherence in strongly underdoped superconducting Bi2Sr2CaCu2O8+δ . Phys. Rev. Lett. 94, 197005 (2005).

    Article  ADS  Google Scholar 

  28. Lee, P. A., Nagaosa, N. & Wen, X.-G. Doping a Mott insulator: Physics of high-temperature superconductivity. Rev. Mod. Phys. 78, 17–85 (2006).

    Article  ADS  Google Scholar 

  29. Hoffman, J. E. et al. Imaging quasiparticle interference in Bi2Sr2CaCu2O8+δ . Science 297, 1148–1151 (2002).

    Article  ADS  Google Scholar 

  30. Tanaka, K. et al. Distinct Fermi-momentum-dependent energy gaps in deeply underdoped Bi2212. Science 314, 1910–1913 (2006).

    Article  ADS  Google Scholar 

  31. Kondo, T., Takeuchi, T., Kaminski, A., Tsuda, S. & Shin, S. Evidence for two energy scales in the superconducting state of optimally doped (Bi,Pb)2(Sr,La)2CuO6+d . Phys. Rev. Lett. 98, 267004 (2007).

    Article  ADS  Google Scholar 

  32. Le Tacon, M. et al. Two energy scales and two distinct quasiparticle dynamics in the superconducting state of underdoped cuprates. Nature Phys. 2, 537–543 (2006).

    Article  ADS  Google Scholar 

  33. Affleck, I. & Marston, J. B. Large-n limit of the Heisenberg–Hubbard model: Implications for high-Tc superconductors. Phys. Rev. B 37, 3774–3777 (1988).

    Article  ADS  Google Scholar 

  34. Zaanen, J. & Gunnarsson, O. Charged magnetic domain lines and the magnetism of high-Tc oxides. Phys. Rev. B 40, 7391–7394 (1989).

    Article  ADS  Google Scholar 

  35. Kampf, A. P. & Schrieffer, J. R. Spectral function and photoemission spectra in antiferromagnetically correlated metals. Phys. Rev. B 42, 7967–7974 (1990).

    Article  ADS  Google Scholar 

  36. Wen, X.-G. & Lee, P. A. Theory of underdoped cuprates. Phys. Rev. Lett. 76, 503–506 (1996).

    Article  ADS  Google Scholar 

  37. Chubukov, A. V., Pines, D. & Stojkovic, B. P. Temperature crossovers in cuprates. J. Phys. Condens. Matter 8, 10017–10036 (1996).

    Article  ADS  Google Scholar 

  38. Varma, C. M. Non-Fermi-liquid states and pairing instability of a general model of copper oxide metals. Phys. Rev. B 55, 14554–14580 (1997).

    Article  ADS  Google Scholar 

  39. Vojta, M. & Sachdev, S. Charge order, superconductivity, and a global phase diagram of doped antiferromagnets. Phys. Rev. Lett. 83, 3916–3919 (1999).

    Article  ADS  Google Scholar 

  40. Chakravarty, S., Laughlin, R. B., Morr, D. K. & Nayak, C. Hidden order in the cuprates. Phys. Rev. B 63, 094503 (2001).

    Article  ADS  Google Scholar 

  41. Paramekanti, A., Randeria, M. & Trivedi, N. Projected wave functions and high temperature superconductivity. Phys. Rev. Lett. 87, 217002 (2001).

    Article  ADS  Google Scholar 

  42. Kivelson, S. A. et al. How to detect fluctuating stripes in the high-temperature superconductors. Rev. Mod. Phys. 75, 1201–1241 (2003).

    Article  ADS  Google Scholar 

  43. Kresin, V. Z., Ovchinnikov, Y. N. & Wolf, S. A. Inhomogeneous superconductivity and the “pseudogap” state of novel superconductors. Phys. Rep. 431, 231–259 (2006).

    Article  ADS  Google Scholar 

  44. Hoffman, J. A search for alternative electronic order in the high temperature superconductor Bi2Sr2CaCu2O8+x by scanning tunneling microscopy. Dissertation, Univ. California, Berkeley (2003).

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Acknowledgements

We thank J. C. Davis, J. E. Hoffman, P. A. Lee, Y. S. Lee, K. McElroy, T. Senthil, Y. Wang and X.-G. Wen for comments. This research was supported in part by a Cottrell Scholarship awarded by the Research Corporation, by the MRSEC program of the NSF under award DMR 02-13282, and also by NSF CAREER award DMR-034891.

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Author notes

  1. Takeshi Kondo

    Present address: Present address: Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA,

Authors and Affiliations

  1. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    M. C. Boyer, W. D. Wise, Kamalesh Chatterjee, Ming Yi, Takeshi Kondo & E. W. Hudson

  2. Department of Crystalline Materials Science, Nagoya University, Nagoya 464-8603, Japan

    Takeshi Kondo, T. Takeuchi & H. Ikuta

  3. EcoTopia Science Institute, Nagoya University, Nagoya 464-8603, Japan

    T. Takeuchi

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Contributions

M.C.B., W.D.W. and K.C. shared equal responsibility for all aspects of this project from instrument construction to data collection and analysis. M.Y. conceived the temperature-normalization scheme and carried out much of the data analysis. T.K. grew the samples and helped refine the STM. T.T. and H.I. contributed to sample growth. E.W.H. advised.

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Correspondence to Takeshi Kondo or E. W. Hudson.

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Boyer, M., Wise, W., Chatterjee, K. et al. Imaging the two gaps of the high-temperature superconductor Bi2Sr2CuO6+x. Nature Phys 3, 802–806 (2007). https://doi.org/10.1038/nphys725

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