Berlin 2008 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 26: Superconductivity: Vortex Dynamics, Vortex Phases, Pinning
TT 26.5: Talk
Wednesday, February 27, 2008, 16:45–17:00, H 3010
Vortex structures in ultra high purity niobium revealed by neutron scattering — •Sebastian Muehlbauer1,2, C. Pfleiderer1, P. Boeni1, A. Wiedenmann3, R. Kampmann4, E. M. Forgan5, and G. Behr6 — 1Physik-Department E21, Technische Universität München, D-85748 Garching — 2Forschungsneutronenquelle Heinz Maier-Leibnitz, FRM II, D-85748 Garching — 3Hahn-Meitner-Institut, D-14109 Berlin — 4Geesthacht Neutron Facility, GKSS, D-21502 Geesthacht — 5School of Physics and Astronomy, Birmingham UK — 6IFW Dresden , D-01171 Dresden
Small angle neutron scattering (SANS) directly maps the vortex lattice (VL) of type II superconductors and gives valuable information on both the underlying Fermi surface and the mechanism of the superconducting pairing. But the symmetry of the VL is also mainly influenced by pinning and impurity effects. Recent studies of the VL in ultra pure samples of the classical superconductor Niobium with field applied along the four-fold (100) axis are showing frustration between the six-fold VL and four-fold crystal symmetry. Four-fold VL patterns additionally breaking the crystal symmetry have been identified in Niobium, which can be partially explained by non-local corrections in the Eilenberger model (1). The symmetry breaking transition is vanishing at a specific rotation angle of the magnetic field versus the (100) axis. As this angle also shows specific features in magnetoresistance, a direct link between the Fermi symmetry and VL symmetry maybe drawn. First experiments benefiting from time-of-flight SANS on VL will be presented. (1) M. Laver et al, Phys. Rev. Lett. 96, 167002 (2006)