OPPOSED (HAMMERHEAD) BIFURCATIONS IN THE RESONANT LINESHAPE OF A STRONGLY DRIVEN SQUID RING-TANK CIRCUIT SYSTEM

In this paper we describe very unusual paired bifurcations which can a ppear in the resonance curve of a coupled SQUID ring-radio frequency ( rf) tank circuit system when the rf flux at the ring is comparable to Phi(0) (= h/2e). We demonstrate that the position of these bistabiliti es is controlled by the static magnetic flux Phi(xstat) applied to the ring, with simple bistable regions being observed on the lower or upp er side of the resonance when (for n integer) Phi(xstat), is close to n Phi(0) or (n + 1/2) Phi(0), respectively. More interestingly, we sho w that for values of Phi(x) close to (n +/- 1/4) Phi(0) this resonance exhibits bistability on both its lower and upper sides. We discuss th is very unusual phenomenon in terms of the non-linear equation of moti on for the coupled system. (C) 1997 Elsevier Science B.V.