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TT: Fachverband Tiefe Temperaturen
TT 32: Postersession Superconductivity: Josephson Junctions, SQUIDs, Heterostructures, Andreev Scattering, Vortex Physics, Cryodetectors, Measuring Devices, Cryotechnique
TT 32.14: Poster
Wednesday, March 25, 2009, 14:00–18:00, P1A
Observation of absolute negative resistance in mesoscopic samples of a-NbGe — •Florian Otto1, Ante Bilušić1,2, Dinko Babić3, Christoph Sürgers4, and Christoph Strunk1 — 1Inst. for Exp. and Appl. Physics, Univ. Regensburg, Germany — 2Fac. of Nat. Sciences, Univ. of Split, Croatia — 3Dept. Physics, Univ. Zagreb, Croatia — 4Phys. Inst. and DFG CFN, Univ. Karlsruhe, Germany
Local and nonlocal measurements on mesoscopic samples of amorphous NbGe, a high-κ type-II superconductor with very low pinning, reveal peculiar features in close vicinity of the transition temperature Tc: in absence of magnetic field, both local and nonlocal DC voltage current characteristics clearly display absolute negative resistance in a small interval around zero current and a small temperature range immediately below Tc . At the same time, a negative voltage is also observed in both local and nonlocal measurements of R(T). The temperatures at which this occurs are consistently found to be around 0.95-0.96 Tc, which is clearly below the narrow superconducting transition region. Upon application of small external magnetic fields on the order of B=50 mT, the effect can be suppressed. The origin of these completely unexpected features is not clear.