Search results for "Joseph"
showing 10 items of 195 documents
Voltage drop across Josephson junctions for L\'evy noise detection
2020
We propose to characterize L\'evy-distributed stochastic fluctuations through the measurement of the average voltage drop across a current-biased Josephson junction. We show that the noise induced switching process in the Josephson washboard potential can be exploited to reveal and characterize L\'evy fluctuations, also if embedded in a thermal noisy background. The measurement of the average voltage drop as a function of the noise intensity allows to infer the value of the stability index that characterizes L\'evy-distributed fluctuations. An analytical estimate of the average velocity in the case of a L\'evy-driven escape process from a metastable state well agrees with the numerical calc…
Enhancement of stability in systems with metastable states
2007
The investigation of noise‐induced phenomena in far from equilibrium systems is one of the approach used to understand the behaviour of physical and biological complex systems. Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The enhancement of the life‐time of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) Ising model (ii) Josephson junction; (iii) stochastic FitzHugh‐Nagumo model; (iv) a population dynamics model, and (v) …
Noise stabilization effects in models of interdisciplinary physics
2009
Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The investigation of noise-induced phenomena in far from equilibrium systems is one of the approaches used to understand the behaviour of physical and biological complex systems. The enhancement of the lifetime of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) polymer translocation dynamics; (ii) transient regime of FitzHugh-Nagumo model; (iii) market stability in a nonlinear …
Flux flow effects in very long Josephson junctions
2000
We report on measurements on very long, L ≃ 30λj, NbAlOxNb underdamped in-line junctions, on which we observed displaced linear slope (DLS) generated by the application of an external magnetic field. We study the behaviour of the branches as a function of the applied magnetic field in terms of both current amplitude and voltage position. The DLS is seen to shift rigidly towards higher voltages when increasing the field, spanning a region roughly centred around the Josephson plasma frequency. We discuss the behaviour of linear branches in terms of one dimensional flux-flow along the extended side of the junction, comparing our data with the results of numerical modeling; from these calculat…
Nonlinear relaxation phenomena in metastable condensed matter systems
2016
Nonlinear relaxation phenomena in three different systems of condensed matter are investigated. (i) First, the phase dynamics in Josephson junctions is analyzed. Specifically, a superconductor-graphene-superconductor (SGS) system exhibits quantum metastable states, and the average escape time from these metastable states in the presence of Gaussian and correlated fluctuations is calculated, accounting for variations in the the noise source intensity and the bias frequency. Moreover, the transient dynamics of a long-overlap Josephson junction (JJ) subject to thermal fluctuations and non-Gaussian noise sources is investigated. Noise induced phenomena are observed, such as the noise enhanced s…
Investigations on the c-axis transport properties of YBa/sub 2/Cu/sub 3/O/sub 7-δ//PrBa/sub 2/Cu/sub 3/O/sub 7-δ/ thin film superlattices
1997
In this paper we report on the c-axis transport properties of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///PrBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superlattices. We describe the preparation, characterisation and patterning of thin film superlattices into suitable mesa structures via standard photolithography. Resistive measurements were carried out which point towards an inhomogenous current distribution in the normal state resistance. Below T/sub c/, the c-axis properties determine the temperature dependent resistance. Resonant tunneling is observed with no Josephson current.
Bi2Sr2Ca2Cu3O10+δ based Josephson junctions and SQUIDs
1996
Josephson junctions and SQUIDs on SrTiO3 bicrystal substrates were prepared from epitaxial Bi2Sr2Ca2Cu3O10+δ thin films with critical temperatures around 95K. The current-voltage characteristics are well described by the resistively and capacitively shunted junction model.I c R n products of 50μV at 77K and 0.7m V at 4.2K have been reached. TheI c (B) dependence is symmetric toB=0 with anI c suppression of 90% in the first minimum. Nevertheless it turns out, that the junctions are inhomogeneous on a μm scale. The flux-voltage transfer function of a SQUID reached 2.7μV/Ф0 at 78K.
Induced unconventional superconductivity on the surface states of Bi2Te3 topological insulator
2017
Topological superconductivity is central to a variety of novel phenomena involving the interplay between topologically ordered phases and broken-symmetry states. The key ingredient is an unconventional order parameter, with an orbital component containing a chiral $p_x$ + i$p_y$ wave term. Here we present phase-sensitive measurements, based on the quantum interference in nanoscale Josephson junctions, realized by using Bi$_2$Te$_3$ topological insulator. We demonstrate that the induced superconductivity is unconventional and consistent with a sign-changing order parameter, such as a chiral $p_x$ + i$p_y$ component. The magnetic field pattern of the junctions shows a dip at zero externally a…
Stabilization Effects of Dichotomous Noise on the Lifetime of theSuperconducting State in a Long Josephson Junction
2015
We investigate the superconducting lifetime of a long overdamped current-biased Josephson junction, in the presence of telegraph noise sources. The analysis is performed by randomly choosing the initial condition for the noise source. However, in order to investigate how the initial value of the dichotomous noise affects the phase dynamics, we extend our analysis using two different fixed initial values for the source of random fluctuations. In our study, the phase dynamics of the Josephson junction is analyzed as a function of the noise signal intensity, for different values of the parameters of the system and external driving currents. We find that the mean lifetime of the superconductive…
Fabrication of Nb-based superconducting single electron transistor
2003
Abstract We have fabricated Nb/(Al-)AlOx/Nb junctions with a single electron transistor (SET) geometry using conventional e-beam lithographic technique. It was possible to reach a clearly defined superconducting gap of 0.75 meV as measured in the current vs. voltage (I–V) characteristic curve, which corresponds to Tc of 4.6 K . The Josephson coupling energy was comparable to the charging energy, EJ≈Ec=30– 40 μeV .