Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Strong coupling between local moments and superconducting ‘heavy’ electrons in UPd2Al3

Abstract

The electronic structure of heavy-fermion compounds arises from the interaction of nearly localized 4f- or 5f-shell electrons (with atomic magnetic moments) with the free-electron-like itinerant conduction-band electrons. In actinide or rare-earth heavy-fermion materials, this interaction yields itinerant electrons having an effective mass about 100 times (or more) the bare electron mass. Moreover, the itinerant electrons in UPd2Al3 are found to be superconducting well below the magnetic ordering temperature1,2 of this compound, whereas magnetism generally suppresses superconductivity in conventional metals. Here we report the detection of a dispersive excitation of the ordered f-electron moments, which shows a strong interaction with the heavy superconducting electrons. This ‘magnetic exciton’ is a localized excitation which moves through the lattice as a result of exchange forces between the magnetic moments. By combining this observation with previous tunnelling measurements on this material3, we argue that these magnetic excitons may produce effective interactions between the itinerant electrons, and so be responsible for superconductivity in a manner analogous to the role played by phonons in conventional superconductors.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Temperature evolution of the inelastic neutron scattering spectrum.
Figure 2: Qualitative evolution of the scattering intensity as a function of the coupling strength.
Figure 3: Tunnelling density of states calculated as function of the applied voltage Vbias for various temperatures.

References

  1. 1

    Geibel, C. et al. Heavy-fermion superconductivity at Tc = 2 K in the antiferromagnet UPd2Al3. Z. Phys. B 84, 1–2 (1991).

    ADS  CAS  Article  Google Scholar 

  2. 2

    Steglich, F. et al. in Proc. Physical Phenomena at High Magnetic Fields-II (eds Fisk, Z., Gor’kov, L., Meltzer, D. & Schrieffer, R.) 125–138 (World Scientific, Singapore, 1996).

    Google Scholar 

  3. 3

    Jourdan, M. et al. Superconductivity mediated by spin fluctuations in the heavy-fermion compound UPd2Al3. Nature 398, 47–49 (1999).

    ADS  CAS  Article  Google Scholar 

  4. 4

    Caspary, R. et al. Unusual ground state properties of UPd2Al3: Implications for the coexistence of heavy fermion superconductivity and local moment antiferromagnetism. Phys. Rev. Lett. 71, 2146–2149 (1993).

    ADS  CAS  Article  Google Scholar 

  5. 5

    Feyerherm, R. et al. Coexistence of local moment magnetism and heavy fermion superconductivity in UPd2Al3. Phys. Rev. Lett. 73, 1849–1852 (1994).

    ADS  CAS  Article  Google Scholar 

  6. 6

    Takahashi, T. et al. Dual character of 5f electrons in UPd2Al3 observed by high-resolution photoemission spectroscopy. J. Phys. Soc. Jpn 65, 156–159 (1996).

    ADS  CAS  Article  Google Scholar 

  7. 7

    Knöpfle, K. et al. The Fermi surface of UPd2Al3. J. Phys. Condens. Matter 8, 901–909 (1996).

    ADS  Article  Google Scholar 

  8. 8

    Yaouanc, A. et al. Study of the uranium 5f shell in UPd2Al3 and URu2Si2 by the x-ray magnetic circular dichroism technique. Phys. Rev. B 58, 8793–8799 (1998).

    ADS  CAS  Article  Google Scholar 

  9. 9

    Yotsuhashi, S., Kusunose, H. & Miyake, K. Orbital dependence in Kondo effect enlarged by Hund's-rule coupling. J. Phys. Soc. Jpn 70, 186–191 (2001).

    ADS  CAS  Article  Google Scholar 

  10. 10

    Sato, N. et al. Spin fluctuations in the heavy fermion superconductor UPd2Al3 studied by neutron inelastic scattering. J. Phys. Soc. Jpn 66, 1884–1887 (1997).

    ADS  CAS  Article  Google Scholar 

  11. 11

    Sato, N. et al. Possible spin-fluctuation mediated superconductivity in UPd2Al3. J. Phys. Soc. Jpn 66, 2981–2984 (1997).

    ADS  CAS  Article  Google Scholar 

  12. 12

    Sato, N. et al. Observation of two low-energy responses in UPd2Al3– interaction of magnetism and superconductivity? J. Alloys Comp. 271–273, 433–436 (1998).

    Article  Google Scholar 

  13. 13

    Bernhoeft, N. et al. Enhancement of magnetic fluctuations on passing below T c in the heavy fermion superconductor UPd2Al3. Phys. Rev. Lett. 81, 4244–4247 (1998).

    ADS  CAS  Article  Google Scholar 

  14. 14

    Mason, T. E. & Aeppli, G. Neutron scattering studies of heavy fermion systems. Mat.-fys. Medd. 45, 231–245 (1997).

    Google Scholar 

  15. 15

    Metoki, N. et al. Superconducting energy gap observed in the magnetic excitation spectra of a heavy fermion superconductor UPd2Al3. Phys. Rev. Lett. 80, 5417–5420 (1998).

    ADS  CAS  Article  Google Scholar 

  16. 16

    Hayden, S. Excitations in exotic superconductors. Phys. World 12(2), 18 (1999).

    CAS  Article  Google Scholar 

  17. 17

    Buyers, W. J. L. & Holden, T. M. in Handbook on the Physics and Chemistry of the Actinides (eds Freeman, A. J. & Lander, G. H.) 239–327 (Elsevier, Amsterdam, 1985).

    Google Scholar 

  18. 18

    Fong, H. F. et al. Phonon and magnetic neutron scattering at 41 meV in YBa2Cu3O7. Phys. Rev. Lett. 75, 316–319 (1995).

    ADS  CAS  Article  Google Scholar 

  19. 19

    Demler, E. et al. π excitation of the t-J model. Phys. Rev. B 58, 5719–5730 (1998).

    ADS  CAS  Article  Google Scholar 

  20. 20

    Kyougaku, M. et al. NMR and NQR studies of magnetism and superconductivity in the antiferromagnetic heavy fermion superconductors UM2Al3 (M=Ni and Pd). J. Phys. Soc. Jpn 62, 4016–4030 (1993).

    ADS  Article  Google Scholar 

  21. 21

    Bernhoeft, N. Superconductor order parameter symmetry in UPd2Al3. Eur. Phys. J. B 13, 685–694 (2000).

    ADS  CAS  Article  Google Scholar 

  22. 22

    Varelogiannis, G. On the limits of consistency of Eliashberg theory and the density of states of high-T c superconductors. Z. Phys. B 104, 411–422 (1997).

    ADS  CAS  Article  Google Scholar 

  23. 23

    Grauel, A. et al. Tetravalency and magnetic phase diagram in the heavy-fermion superconductor UPd2Al3. Phys. Rev. B 46, 5818–5821 (1992).

    ADS  CAS  Article  Google Scholar 

  24. 24

    Schenck, A. et al. Study of the positive muon Knight shift in UNi2Al3: evidence for a tetravalent U4+-state and crystalline electric field (CEF) splitting. Eur. Phys. J. B 13, 245–256 (2000).

    ADS  CAS  Article  Google Scholar 

  25. 25

    Krimmel, A. et al. Magnetic excitations and the search for crystal-field transitions in the heavy-fermion superconductor UPd2Al3. J. Phys. Condens. Matter. 8, 1677–1685 (1996).

    ADS  CAS  Article  Google Scholar 

Download references

Acknowledgements

Neutron scattering experiments were performed in collaboration with G. H. Lander, B. Roessli, N. Bernhoeft, A. Hiess, Y. Endoh, and with the help of the cryogenic and technical staffs of ILL, Grenoble. We thank O. Sakai, M. Lang, N. Bernhoeft, G. H. Lander and T. Dahm for discussions and comments, and D. Preston and M. Grosche for a critical reading of the manuscript. N. K. S. is supported by a Grant-in-Aid from the Ministry of Education, Science, Sports and Culture, Japan, and K. M. is supported by the COE project of Monbusho, Japan.

Author information

Affiliations

Authors

Corresponding author

Correspondence to N. K. Sato.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Sato, N., Aso, N., Miyake, K. et al. Strong coupling between local moments and superconducting ‘heavy’ electrons in UPd2Al3. Nature 410, 340–343 (2001). https://doi.org/10.1038/35066519

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing