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# 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.

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## 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).

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).

3. 3

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

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).

5. 5

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

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).

7. 7

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

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).

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).

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).

11. 11

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

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).

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).

14. 14

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

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).

16. 16

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

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).

18. 18

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

19. 19

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

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).

21. 21

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

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).

23. 23

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

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).

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).

## 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.

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Correspondence to N. K. Sato.

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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

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