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TT: Tiefe Temperaturen

TT 18: Superconductivity: Borides, Borocarbides, Carbides, ...

TT 18.10: Vortrag

Dienstag, 28. März 2006, 17:30–17:45, HSZ 02

The Fermi surface topology and the superconducting gap function in UPd₂Al₃: a neutron spin-echo study — •Arno Hiess¹, Elizabeth Blackburn^1,2, Maikel C. Rheinstädter¹, Wolfgang Häußler^1,3, Nicholas Bernhoeft⁴, and Gerry H. Lander² — ¹Institut Laue-Langevin, BP 156, F-38042 Grenoble, France — ²European Commission, JRC, ITU, Postfach 2340, D-76125 Karlsruhe, Germany — ³FRM-II, TU München, D-85748 Garching, Germany — ⁴DRFMC, CEA-Grenoble, F-38054 Grenoble, France

We report on a single crystal neutron spin-echo investigation of the low-energy dynamic response in the magnetic superconductor UPd₂Al₃ (T_N = 14 K, T_sc = 2 K) in the vicinity of the antiferromagnetic wavevector Q₀ = (0 0 0.5). Well inside the superconducting phase, antiferromagnetic quasielastic scattering, which is present in the normal state, is absent for relaxation times shorter than 10 ns, equivalent to an energy resolution better than 1 µeV. These observations are related to the geometry of the gap function and the Fermi surface topology. Any nodes present at the Fermi surface do not contribute significant weight to the electronic susceptibility. This places strong constraints on possible models for the origin and role of magnetic excitations in this magnetic superconductor.