Regensburg 2010 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 9: SC: Poster Session

TT 9.45: Poster

Montag, 22. März 2010, 14:00–18:00, Poster A

Experimental Test for “Münchhausen Effect” in an Asymmetric dc-SQUID — •Susanne Butz, Kirill G. Fedorov, Alexey K. Feofanov, and Alexey V. Ustinov — Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany

We will report experiments aimed at observation of the so called “Münchhausen effect” - a coupling of one classical and one quantum mechanical degree of freedom. It has been theoretically predicted in [1] that this effect can be realised in an asymmetric dc-SQUID. The two junctions in the superconducting loop are made to have the same critical current but different capacitances. This creates a system with strongly asymmetric dynamical parameters. The capacitively shunted junction behaves classically and thus cannot tunnel out of a metastable state. In turn, the quantum mechanical junction can leave its metastable minimum via macroscopic quantum tunneling. This process distorts the potential for the classical junction resulting in an effective decrease of the potential barrier height. If the coupling between the juntions is strong enough this distortion is sufficient to turn the metastable minimum into an inflection point of the classical junction.

We will report switching current histograms taken and investigated for different dc-SQUID parameters, temperatures and flux biases. In addition we performed numerical simulations using classical noise and compared the results with experimental data.

[1] A.U. Thomann, V.B. Geshkenbein and G. Blatter, Phys. Rev. B 79, 184515 (2009).