E. Goldobin

Josephson vortex in a ratchet potential: Theory

We propose a type of Josephson vortex ratchet. In this system a Josephson vortex moves in a periodic asymmetric potential under the action of a deterministic or random force with zero time average. For some implementations the amplitude of the potential can be controlled during the experiment, thus allowing us to tune the performance of the system and build rocking as well as flashing ratchets. We discuss the differences between conventional and Josephson vortex ratchets and present a model describing the dynamics of the fluxon in such a system. We show numerical simulation results that predict rectification of a monochromatic, deterministic signal with zero time average. The investigation of this system may lead to the development of the fluxon rectifier-a device that produces a dc voltage from nonequilibrium fluctuations.

Cherenkov Radiation from Fluxon in a Stack of Coupled Long Josephson Junctions

We present a systematic study of the Cherenkov radiation of Josephson plasma waves by fast moving fluxon in a stack of coupled long Josephson junctions for different fluxon modes. It is found that at some values of parameters current-voltage characteristic may exhibit a region of the back-bending on the fluxon step. In the opposite limit the emission of the Cherenkov radiation takes place. In the annular junctions of moderate length the interaction of the emitted waves with fluxon results in the novel resonances which emerge on the top of the fluxon step. We present more exact formulas which describe the position of such resonances taking into account difference between junction and non-linear corrections. The possibility of direct detection of the Cherenkov radiation in junctions of linear geometry is discussed.

NUMERICAL ANALYSIS OF THE COHERENT RADIATION EMISSION BY TWO STACKED JOSEPHSON FLUX-FLOW OSCILLATORS

The numerical investigation of the radiation emission by a system of two magnetically coupled, long Josephson junctions is reported. Time‐dependent synchronized voltage response in the flux‐flow regime is analyzed for the case of in‐phase and out‐of‐phase oscillations in the junctions. Simulations show that Josephson junctions operating in the in‐phase flux‐flow mode may generate rf radiation power by a factor of more than 4 larger than that of a single Josephson junction. The radiation in the out‐of‐phase flux‐flow mode is characterized by nearly completely suppressed amplitudes of odd harmonics and considerably damped even harmonics as compared to that of a single barrier junction. The dependence of the radiation power on the parameter spread between the junctions is investigated. The advantages of using stacked Josephson junctions as oscillators for the sub‐mm wave band are discussed.

Method for reliable realization of a ϕ Josephson junction

We propose a method to realize a

Nonideal artificial phase discontinuity in long Josephson 0-κ junctions

phi

Progressive motion of an ac-driven kink in an annular damped system

Josephson junction by combining alternating 0 and

Bunching of fluxons by Cherenkov radiation in Josephson multilayers

pi

Tunable±φ,φ0, andφ0±φJosephson junction

parts (sub junctions) with an intrinsically non-sinusoidal current-phase relation (CPR). Conditions for the realization of the

ac-induced damping of a fluxon in a long Josephson junction

phi

Maximum velocity of a fluxon in a stack of coupled Josephson junctions

ground state are analyzed. It is shown that taking into account the non-sinusoidal CPR for a clean junction with a ferromagnetic (F) barrier, one can significantly enlarge the domain (regime of suitable F-layer thicknesses) of the