Berlin 2008 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 21: Nonlinear dynamics, synchronization and chaos III
DY 21.2: Vortrag
Mittwoch, 27. Februar 2008, 17:00–17:15, MA 001
Absolute negative resistance in Josephson junctions — •Joachim Nagel1, Tobias Gaber1, David Speer2, Ralf Eichhorn2, Peter Reimann2, Reinhold Kleiner1, and Dieter Koelle1 — 1Universität Tübingen, Physikalisches Institut – Experimentalpysik II — 2Universität Bielefeld, Fakultät für Physik
It has been predicted [1,2] that an underdamped Brownian particle, moving in a periodic 1D potential under the influence of both, a dc and ac driving force, can show absolute negative mobility (ANM), i. e., the particle moves opposite to the dc drive. Here, we present the experimental realization of this effect, using underdamped Nb−AlOx−Nb Josephson junctions, irradiated with microwaves up to ∼ 40 GHz. In this system, described by the resistively and capacitively shunted junction model, the particle coordinate, its average velocity and the driving forces correspond to the Josephson phase, a dc voltage V, and applied dc and ac currents, respectively. Measuring the dc I−V curves at 4.2 K, we demonstrate the appearance of ANM, or in our system, of absolute negative resistance (ANR) and determine its dependence on amplitude and frequency of the ac drive. As pointed out in [1], there are two basically different physical mechanism giving rise to ANM: one is governed by transient chaos [1], while the other essentially amounts to a noise induced effect [2]. Comparison of the experimental data with numerical simulations shows very good agreement and implies that the basic physical mechanism from [1] is at work in the present system.
[1] Speer et al., Europhys. Lett. 79, 10005; Phys. Rev. E 76, 051110 (2007). [2] L. Machura et al., Phys. Rev. Lett. 98, 040601 (2007).