A distinct bosonic mode in an electron-doped high-transition-temperature superconductor

Abstract

Despite recent advances in understanding high-transition-temperature (high-Tc) superconductors, there is no consensus on the origin of the superconducting ‘glue’: that is, the mediator that binds electrons into superconducting pairs. The main contenders are lattice vibrations1,2 (phonons) and spin-excitations3,4, with the additional possibility of pairing without mediators5. In conventional superconductors, phonon-mediated pairing was unequivocally established by data from tunnelling experiments6. Proponents of phonons as the high-Tc glue were therefore encouraged by the recent scanning tunnelling microscopy experiments on hole-doped Bi2Sr2CaCu2O8-δ (BSCCO) that reveal an oxygen lattice vibrational mode whose energy is anticorrelated with the superconducting gap energy scale7. Here we report high-resolution scanning tunnelling microscopy measurements of the electron-doped high-Tc superconductor Pr0.88LaCe0.12CuO4 (PLCCO) (Tc = 24 K) that reveal a bosonic excitation (mode) at energies of 10.5 ± 2.5 meV. This energy is consistent with both spin-excitations in PLCCO measured by inelastic neutron scattering (resonance mode)8 and a low-energy acoustic phonon mode9, but differs substantially from the oxygen vibrational mode identified in BSCCO. Our analysis of the variation of the local mode energy and intensity with the local gap energy scale indicates an electronic origin of the mode consistent with spin-excitations rather than phonons.

Access options

Rent or Buy article

from\$8.99

All prices are NET prices.

References

1. 1

McQueeney, R. J. et al. Anomalous dispersion of LO phonons in La1. 85Sr0. 15CuO4 at low temperatures. Phys. Rev. Lett. 82, 628–631 (1999)

2. 2

Lanzara, A. et al. Evidence for ubiquitous strong electron–phonon coupling in high-temperature superconductors. Nature 412, 510–514 (2001)

3. 3

Rossat-Mignod, J. et al. Neutron scattering study of the YBa2Cu3O6+x system. Physica C 185–189, 86–92 (1991)

4. 4

Norman, M. R. et al. Unusual dispersion and line shape of the superconducting state spectra of Bi2Sr2CaCu2O8+δ . Phys. Rev. Lett. 79, 3506–3509 (1997)

5. 5

Anderson, P. W. Is there glue in cuprate superconductors? Science 316, 1705–1707 (2007)

6. 6

McMillan, W. L. & Rowell, J. M. Lead phonon spectrum calculated from superconducting density of states. Phys. Rev. Lett. 14, 108–112 (1965)

7. 7

Lee, J. et al. Interplay of electron-lattice interactions and superconductivity in Bi2Sr2CaCu2O8+δ . Nature 442, 546–550 (2006)

8. 8

Wilson, S. D. et al. Resonance in the electron-doped high-transition-temperature superconductor Pr0. 88LaCe0. 12CuO4–δ . Nature 442, 59–62 (2006)

9. 9

d’Astuto, M. et al. Anomalous dispersion of longitudinal optical phonons in Nd1. 86Ce0. 14CuO4+δ determined by inelastic X-ray scattering. Phys. Rev. Lett. 88, 167002 (2002)

10. 10

Pan, Z.-H. et al. Universal quasiparticle decoherence in hole- and electron-doped high-T c cuprates. Preprint at 〈http://www.arXiv.org/cond-mat/0610442〉 (2006)

11. 11

Kashiwaya, S. et al. Tunneling spectroscopy of superconducting Nd1. 85Ce0. 15CuO4–δ . Phys. Rev. B 57, 8680–8686 (1998)

12. 12

Littlewood, P. B. & Varma, C. M. Anisotropic tunneling and resistivity in high-temperature superconductors. Phys. Rev. B 45, 12636 (1992)

13. 13

Kirtley, J. R. & Scalapino, D. J. Inelastic-tunneling model for the linear conductance background in the high-T c superconductors. Phys. Rev. Lett. 65, 798–800 (1990)

14. 14

Matsui, H. et al. Direct observation of a nonmonotonic d x 2 − y 2 -wave superconducting gap in the electron-doped high-Tc superconductor Pr0. 89LaCe0. 11CuO4 . Phys. Rev. Lett. 95, 017003 (2005)

15. 15

Shan, L. et al. An universal law of the superconducting gap in the electron-doped cuprate superconductors. Phys. Rev. B (in the press). Preprint at 〈http://www.arXiv.org/cond-mat/0703256〉 (2007)

16. 16

Pilgram, S., Rice, T. M. & Sigrist, M. Role of inelastic tunneling through the insulating barrier in scanning-tunneling-microscope experiments on cuprate superconductors. Phys. Rev. Lett. 97, 117003 (2006)

17. 17

Zhao, J. et al. Neutron-spin resonance in optimally electron-doped superconductor Nd1. 85Ce0. 15CuO4 . Phys. Rev. Lett. 99, 017001 (2007)

18. 18

Zhu, J. X. et al. Fourier-transformed local density of states and tunneling into a d-wave superconductor with bosonic modes. Phys. Rev. B 73, 014511 (2006)

19. 19

Lavrov, A. N. et al. Spin-flop transition and the anisotropic magnetoresistance of Pr1. 3-xLa0. 7CexCuO4: Unexpectedly strong spin-charge coupling in the electron doped cuprates. Phys. Rev. Lett. 92, 227003 (2004)

20. 20

Pintschovius, L. et al. Inelastic neutron scattering study of La2CuO4 . Prog. High Temp. Supercond. 21, 36–45 (1989)

21. 21

Renker, B. et al. Electron–phonon coupling in HTC superconductors evidenced by inelastic neutron scattering. Physica B 180, 450–452 (1992)

22. 22

Pintschovius, L. & Reichardt, W. in Physical Properties of High Temperature Superconductors Vol. IV (ed. Ginsberg, D. M.) 295 (World Scientific, London, 1994)

23. 23

Crawford, M. K. et al. Infrared active phonons in (Pr2–x Ce x )CuO4 . Solid State Commun. 73, 507–509 (1990)

24. 24

Homes, C. C. et al. Optical properties of Nd1. 85Ce0. 15CuO4 . Phys. Rev. B 56, 5525–5534 (1997)

25. 25

Lynn, J. W. et al. Phonon density of states and superconductivity in Nd1. 85Ce0. 15CuO4 . Phys. Rev. Lett. 66, 919–922 (1991)

26. 26

Persson, B. N. J. & Baratoff, A. Inelastic electron tunneling from a metal tip: the contribution from resonant processes. Phys. Rev. Lett. 59, 339–342 (1987)

27. 27

Hwang, J., Timusk, T. & Carbotte, J. P. Scanning-tunneling spectra of cuprates. Nature 446, E3–E4 (2007)

28. 28

Scalapino, D. J. Superconductivity: Pairing glue or inelastic tunnelling? Nature Phys. 2, 593–594 (2006)

29. 29

Eliashberg, G. M. Interactions between electrons and lattice vibrations in a superconductor. Sov. Phys. JETP 11, 696–702 (1960)

Acknowledgements

We thank A. V. Balatsky, E. W. Hudson, P. Richard, G. Murthy, J. Engelbrecht and J. C. Davis for discussions and comments. This work was supported by the NSF and the DOE.

Author information

Correspondence to V. Madhavan.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-5 with Legends and a brief summary of experimental parameters and methods. (PDF 3524 kb)

Rights and permissions

Reprints and Permissions

Niestemski, F., Kunwar, S., Zhou, S. et al. A distinct bosonic mode in an electron-doped high-transition-temperature superconductor. Nature 450, 1058–1061 (2007) doi:10.1038/nature06430

• Detection of Bosonic Mode as a Signature of Magnetic Excitation in One-Unit-Cell FeSe on SrTiO3

• Chaofei Liu
• , Ziqiao Wang
• , Shusen Ye
• , Cheng Chen
• , Yi Liu
• , Qingyan Wang
• , Qiang-Hua Wang
•  & Jian Wang

Nano Letters (2019)

• Bosonic excitations and electron pairing in an electron-doped cuprate superconductor

• M. C. Wang
• , H. S. Yu
• , J. Xiong
• , Y.-F. Yang
• , S. N. Luo
• , K. Jin
•  & J. Qi

Physical Review B (2018)

• Distinction between critical current effects and intrinsic anomalies in the point-contact Andreev reflection spectra of unconventional superconductors

• Ge He
• , Zhong-Xu Wei
• , Jérémy Brisbois
• , Yan-Li Jia
• , Yu-Long Huang
• , Hua-Xue Zhou
• , Shun-Li Ni
• , Alejandro V Silhanek
• , Lei Shan
• , Bei-Yi Zhu
• , Jie Yuan
• , Xiao-Li Dong
• , Fang Zhou
• , Zhong-Xian Zhao
•  & Kui Jin

Chinese Physics B (2018)

• Unconventional superconductivity

• G. R. Stewart

Advances in Physics (2017)

• Coexistence of Weak and Strong Coupling Mechanism, in an Iron-Based Superconductor FeSe 0.5 Te 0.5: Possible Signature of BCS-BEC Crossover

• S. Kunwar
• , R. M. Hamad
•  & Kh. A. Ziq

Journal of Superconductivity and Novel Magnetism (2017)