UPd2Al3

UPd2Al3 is a heavy-fermion superconductor with a hexagonal crystal structure and critical temperature Tc=2.0K that was discovered in 1991.[1] Furthermore, UPd2Al3 orders antiferromagnetically at TN=14K, and UPd2Al3 thus features the unusual behavior that this material, at temperatures below 2K, is simultaneously superconducting and magnetically ordered. Later experiments demonstrated that superconductivity in UPd2Al3 is magnetically mediated,[2] and UPd2Al3 therefore serves as a prime example for non-phonon-mediated superconductors.

Discovery

Heavy-fermion superconductivity was discovered already in the late 1970s (with CeCu2Si2 being the first example), but the number of heavy-fermion compounds known to superconduct was still very small in the early 1990s, when Christoph Geibel in the group of Frank Steglich found two closely related heavy-fermion superconductors, UNi2Al3 (Tc=1K) and UPd2Al3 (Tc=2K), which were published in 1991.[3][1] At that point, the Tc=2.0K of UPd2Al3 was the highest critical temperature amongst all know heavy-fermion superconductors, and this record would stand for 10 years until CeCoIn5 was discovered in 2001.[4]

Superconducting state

Superconductivity in UPd2Al3 has a critical temperature of 2.0K and a critical field around 3T. For heavy-fermion superconductors it is generally believed that coupling mechanism cannot be phononic in nature. In contrast to many other unconventional superconductors, for UPd2Al3 there actually exists strong experimental evidence (namely from neutron scattering [2] and tunneling spectroscopy [5]) that superconductivity is magnetically mediated.

References

  1. 1 2 Geibel, C.; Schank, C.; Thies, S.; Kitazawa, H.; Bredl, C.D.; Böhm, A.; Rau, M.; Grauel, A.; Caspary, R.; Helfrich, R.; Ahlheim, U.; Weber, G.; Steglich, F. (1991). "Heavy-fermion superconductivity at Tc=2K in the antiferromagnet UPd2Al3". Z. Phys. B. 84: 1. doi:10.1007/BF01453750.
  2. 1 2 Sato, N.K.; Aso, N.; Miyake, K.; Shiina, R.; Thalmeier, P.; Varelogiannis, G.; Geibel, C.; Steglich, F.; Fulde, P.; Komatsubara, T. (2001). "Strong coupling between local moments and superconducting 'heavy' electrons in UPd2Al3". Nature. 410: 340. doi:10.1038/35066519.
  3. ↑ Geibel, C.; Thies, S.; Kaczorowski, D.; Mehner, A.; Grauel, A.; Seidel, B.; Ahlheim, U.; Helfrich, R.; Petersen, K.; Bredl, C.D.; Steglich, F. (1991). "A new heavy-fermion superconductor: UNi2Al3". Z. Phys. B. 83: 305. doi:10.1007/BF01313397.
  4. ↑ Petrovic, C.; Pagliuso, P.G.; Hundley, M.F.; Movshovich, R.; Sarrao, J.L.; Thompson, J.D.; Fisk, Z.; Monthoux, P. (2001). "Heavy-fermion superconductivity in CeCoIn5 at 2.3 K". J. Phys.: Condens. Matter. 13: L337. arXiv:cond-mat/0103168Freely accessible. doi:10.1088/0953-8984/13/17/103.
  5. ↑ Jourdan, M.; Huth, M.; Adrian, H. (1999). "Superconductivity mediated by spin fluctuations in the heavy-fermion compound UPd2Al3". Nature. 398: 47. doi:10.1038/17977.
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