Josephson junction ratchet: The impact of finite capacitances

Jakub Spiechowicz, Peter Hänggi, and Jerzy Łuczka
Phys. Rev. B 90, 054520 – Published 27 August 2014

Abstract

We study transport in an asymmetric superconducting quantum interference device (SQUID) which is composed of a loop with three capacitively and resistively shunted Josephson junctions: two in series in one arm and the remaining one in the other arm. The loop is threaded by an external magnetic flux and the system is subjected to both a time-periodic and a constant current. We formulate the deterministic and, as well, the stochastic dynamics of the SQUID in terms of the Stewart-McCumber model and derive an equation for the phase difference across one arm, in which an effective periodic potential is of the ratchet type, i.e., its reflection symmetry is broken. In doing so, we extend and generalize an earlier study by Zapata et al. [Phys. Rev. Lett. 77, 2292 (1996)] and analyze directed transport in wide parameter regimes: covering the overdamped to the moderate damping regime up to its fully underdamped regime. As a result we detect the intriguing features of a negative (differential) conductance, repeated voltage reversals, noise-induced voltage reversals, and solely thermal noise-induced ratchet currents. We identify a set of parameters for which the ratchet effect is most pronounced and show how the direction of transport can be controlled by tailoring the external magnetic flux.

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  • Received 1 July 2014
  • Revised 11 August 2014

DOI:https://doi.org/10.1103/PhysRevB.90.054520

©2014 American Physical Society

Authors & Affiliations

Jakub Spiechowicz1, Peter Hänggi2,3, and Jerzy Łuczka1,4

  • 1Institute of Physics, University of Silesia, 40-007 Katowice, Poland
  • 2Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany
  • 3Nanosystems Initiative Munich, Schellingstrasse 4, D-80799 München, Germany
  • 4Silesian Center for Education and Interdisciplinary Research, University of Silesia, 41-500 Chorzów, Poland

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Issue

Vol. 90, Iss. 5 — 1 August 2014

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