Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session

TT 33.45: Poster

Mittwoch, 28. März 2012, 15:00–19:00, Poster B

Cooper pair and quasiparticle transport in Josephson junction chains — •Roland Schäfer², Andreas Fiebig¹, Birgit Kießig^2,1, Hannes Rotzinger¹, and Alexey V. Ustinov¹ — ¹Physikalisches Institut, Karlsruhe Institute of Technology — ²Institut für Festkörperphysik, Karlsruhe Institue of Technology

We present measurements of IV characteristics of daisy-chained mesoscopic SQUID loops where the charging energy is of the same order as the Josephson coupling energy at zero magnetic field. At low voltages the transport is suppressed to a level below the detection limit. Above a threshold V_sw the system jumps to a resistive brunch. The effective Josephson coupling along the chain can be modulated by a magnetic field. The field dependence of the IV characteristics gives evidence that the current is carried dominantly by Cooper pairs. Yet, the smooth transition to quasiparticle dominated transport at large bias hints towards a dissipation mechanism that involves generation and incoherent transport of the latter at any finite current even for voltages well bellow 2NΔ, where N is the number of Josephson junctions in the chain and Δ is the superconducting energy gap.