Torus fractalization and singularities in the current-voltage characteristics for the quasiperiodically forced Josephson junction

¹ Institute of Radio-Engineering and Electronics of RAS, Saratov Division Zelenaya 38, Saratov, Russian Federation
² Department of Physics, University of Potsdam Am Neuen Palais 10, PF 601553, D-14415 Potsdam, Germany

Received: 20 June 2002
Accepted: 18 October 2002

Abstract

We consider a model of Josephson junction driven by a two-frequency quasiperiodic field. In dependence on the amplitude of one frequency component, the transition from a state with zero average voltage to that with a nonzero voltage occurs via the appearance of an intermittent regime, represented either by a smooth torus, or by a strange nonchaotic attractor. The intermediate situation corresponds to the torus fractalization, and the bifurcation there consists in coalescence with further disappearance of a pair of stable and unstable wrinkled invariant curves. We demonstrate different types of singularities in the current-voltage characteristics: in the subcritical case it is associated with the trivial exponent , and the criticality with the nontrivial exponent .