Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 27: Superconductivity: Vortex Dynamics, Vortex Phases, Pinning
TT 27.3: Vortrag
Mittwoch, 25. März 2009, 14:30–14:45, HSZ 105
Interplay of thermomagnetic and nonequilibrium effects in nonlocal vortex transport in mesoscopic NbGe channels — •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
Amorphous Nb0.7Ge0.3, a high-κ type-II superconductor with very low pinning, allows for measurements in the flux-flow regime over large parts of the B-T-phase diagram. When a transport current is driven through a narrow wire (width 250 nm) connected to remote voltage probes via a perpendicular channel (length 2 µ m) in presence of an external (out-of-plane) magnetic field, the Transversal Flux Transformer Effect can be used to produce a nonlocal voltage drop on the remote contacts caused by vortex motion in the channel. In the simplest picture, the Lorentz force acting on the vortices in the local wire creates a pressure on the vortices in the channel, such that the mutual vortex repulsion can explain the nonlocal vortex motion. However, detailed measurements of nonlocal DC voltage-current characteristics taken across the whole B-T-plane show several new aspects, including abrupt sign reversals of the vortex motion. This can be understood in terms of an interplay between Lorentz force (low currents) and Nernst effect via local electron heating (high currents) for T≪ Tc, and between the Lorentz force (low currents) and a force due to the local suppression of the superconducting gap (high currents) for T close to Tc.