494 research outputs found
Frequency-domain analysis of the periodically-forced Josephson-junction circuit
In this paper, a new frequency domain technique to analyze the Josephson-junction circuit dynamics is presented. This technique overcomes some of the limitations inherent to the analytical and time-integration techniques used in previous works. The technique can be extended to the analysis of this device when combined with distributed elements in microwave systems. It allows an efficient analysis of the different types of steady-state solutions and the bifurcation loci in the presence of a periodic driving current source. No restriction is imposed to the driving source amplitude, enabling an accurate analysis of the influence of this parameter on the device superconducting properties. The technique has also been applied to analyze the quasi-periodic states present in this device together with the synchronized solutions to the driving current source.This work was supported by the Spanish Ministry of Economy and Competitiveness
under Contract TEC2011-29264-C03-01
Metastability in a nano-bridge based hysteretic DC-SQUID embedded in superconducting microwave resonator
We study the metastable response of a highly hysteretic DC-SQUID made of a
Niobium loop interrupted by two nano-bridges. We excite the SQUID with an
alternating current and with direct magnetic flux, and find different stability
zones forming diamond-like structures in the measured voltage across the SQUID.
When such a SQUID is embedded in a transmission line resonator similar diamond
structures are observed in the reflection pattern of the resonator. We have
calculated the DC-SQUID stability diagram in the plane of the exciting control
parameters, both analytically and numerically. In addition, we have obtained
numerical simulations of the SQUID equations of motion, taking into account
temperature variations and non-sinusoidal current-phase relation of the
nano-bridges. Good agreement is found between experimental and theoretical
results
Dynamical Instabilities and Deterministic Chaos in Ballistic Electron Motion in Semiconductor Superlattices
We consider the motion of ballistic electrons within a superlattice miniband
under the influence of an alternating electric field. We show that the
interaction of electrons with the self-consistent electromagnetic field
generated by the electron current may lead to the transition from regular to
chaotic dynamics. We estimate the conditions for the experimental observation
of this deterministic chaos and discuss the similarities of the superlattice
system with the other condensed matter and quantum optical systems.Comment: 6 pages, RevTEX; 4 fig
Analytical and Numerical Analysis of Linear and Nonlinear Properties of an rf-SQUID Based Metasurface
We derive a model to describe the interaction of an rf-SQUID (radio frequency
superconducting quantum interference device) based metasurface with free space
electromagnetic waves. The electromagnetic fields are described on the base of
Maxwell's equations. For the rf-SQUID metasurface we rely on an equivalent
circuit model. After a detailed derivation, we show that the problem that is
described by a system of coupled differential equations is wellposed and,
therefore, has a unique solution. In the small amplitude limit, we provide
analytical expressions for reflection, transmission, and absorption depending
on the frequency. To investigate the nonlinear regime, we numerically solve the
system of coupled differential equations using a finite element scheme with
transparent boundary conditions and the Crank-Nicolson method. We also provide
a rigorous error analysis that shows convergence of the scheme at the expected
rates. The simulation results for the adiabatic increase of either the field's
amplitude or its frequency show that the metasurface's response in the
nonlinear interaction regime exhibits bistable behavior both in transmission
and reflection.Comment: published in Physical Review B, Phys. Rev. B 99, 07540
Towards single-electron metrology
We review the status of the understanding of single-electron transport (SET)
devices with respect to their applicability in metrology. Their envisioned role
as the basis of a high-precision electrical standard is outlined and is
discussed in the context of other standards. The operation principles of single
electron transistors, turnstiles and pumps are explained and the fundamental
limits of these devices are discussed in detail. We describe the various
physical mechanisms that influence the device uncertainty and review the
analytical and numerical methods needed to calculate the intrinsic uncertainty
and to optimise the fabrication and operation parameters. Recent experimental
results are evaluated and compared with theoretical predictions. Although there
are discrepancies between theory and experiments, the intrinsic uncertainty is
already small enough to start preparing for the first SET-based metrological
applications.Comment: 39 pages, 14 figures. Review paper to be published in International
Journal of Modern Physics
Colloquium: Quantum and Classical Discrete Time Crystals
The spontaneous breaking of time translation symmetry has led to the
discovery of a new phase of matter - the discrete time crystal. Discrete time
crystals exhibit rigid subharmonic oscillations, which result from a
combination of many-body interactions, collective synchronization, and
ergodicity breaking. This Colloquium reviews recent theoretical and
experimental advances in the study of quantum and classical discrete time
crystals. We focus on the breaking of ergodicity as the key to discrete time
crystals and the delaying of ergodicity as the source of numerous phenomena
that share many of the properties of discrete time crystals, including the AC
Josephson effect, coupled map lattices, and Faraday waves. Theoretically, there
exists a diverse array of strategies to stabilize time crystalline order in
both closed and open systems, ranging from localization and prethermalization
to dissipation and error correction. Experimentally, many-body quantum
simulators provide a natural platform for investigating signatures of time
crystalline order; recent work utilizing trapped ions, solid-state spin
systems, and superconducting qubits will be reviewed. Finally, this Colloquium
concludes by describing outstanding challenges in the field and a vision for
new directions on both the experimental and theoretical fronts.Comment: 29 pages, 13 figures; commissioned review for Reviews of Modern
Physic
Influence of Bifurcation Structures Revealed by Refinement of a Nonlinear Conductance in JosephsonJunction Element
We conduct a bifurcation analysis of a single-junction superconducting quantum interferometer with an external flux. We approximate the current-voltage characteristics of the conductance in the equivalent circuit of the JJ by using two types of functions: a linear function and a piecewise linear (PWL) function. We describe a method to compute the local stability of the solution orbit and to solve the bifurcation problem. As a result, we reveal the bifurcation structure of the systems in a two-dimensional parameter plane. By making a comparison between the linear and PWL cases, we find a difference in the shapes of their bifurcation sets in the two-dimensional parameter plane even though there are no differences in the one-dimensional bifurcation diagrams or the trajectories. As for the influence of piecewise linearization, we discovered that grazing bifurcations terminate the calculation of the local bifurcations, because they drastically change the stability of the periodic orbit
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