1,721,030 research outputs found
THE ROLE OF NON-GAUSSIAN SOURCES IN THE TRANSIENT DYNAMICS OF LONG JOSEPHSON JUNCTIONS
Full text linkWe analyze the effects of different non-Gaussian noise sources on the transient dynamics of an overdamped long Josephson junction. We find nonmonotonic behavior of the mean escape time as a function of the noise intensity and frequency of the external driving signal for all the noise sources investigated
Josephson-based Threshold Detector for Lévy-Distributed Current Fluctuations
No full textWe propose a threshold detector for Levy-distributed fluctuations based on a Josephson junction. The Levy-noise current added to a linearly ramped bias current results in clear changes in the distribution of switching currents out of the zero-voltage state of the junction. We observe that the analysis of the cumulative distribution function of the switching currents supplies information on both the characteristics' shape parameter alpha of the Levy statistics. Moreover, we discuss a theoretical model, which allows characteristic features of the Levy fluctuations to be extracted from a measured distribution of switching currents. In view of these results, this system can effectively find an application as a detector for a Levy signal embedded in a noisy background
Thermoelectric signatures of order-parameter symmetries in iron-based superconducting tunnel junctions
Full text linkThermoelectrical properties are frequently used to characterize the materials
and endow the free energy from wasted heat for useful purposes. Here, we show
that linear thermoelectric effects in tunnel junctions with Fe-based
superconductors, not only address the dominance between particle and hole
states, but even provide information about the superconducting order parameter
symmetry. In particular, we observe that nodal order parameters present a
maximal thermoelectric effect at lower temperatures than for nodeless cases.
Furthermore, we show also that superconducting tunnel junctions between
Fe-based and BCS superconductors could provide a thermoelectric efficiency ZT
exceeding 6 with a linear Seebeck coefficient around at a few Kelvin. These results pave the way to novel
thermoelectric machines based on multi-band superconductors.Comment: Editors' Suggestion. Letter. Main Text 7 pages, 3 figures.
Supplemental Material 8 pages, 9 figure
Topological Phase Diagram of an Interacting Kitaev Chain: Mean Field versus DMRG Study
No full textIn this work, we study the topological phase transitions of a Kitaev chain generalized by the addition of nearest-neighbor Coulomb interaction. We show the presence of a robust topological phase as a function of the interaction strength and of the on-site energy with associated non-zero energy Majorana states localized at the chain edges. We provide an effective mean-field model that allows for the self-consistent computation of the mean value of the local particle number operator, and we also perform Density Matrix Renormalization Group numerical simulations based on a tensor network approach. We find that the two methods show a good agreement in reporting the phase transition between trivial and topological superconductivity. Temperature robustness within a physically relevant threshold has also been demonstrated. These findings shed light on an entire class of topological interacting one-dimensional systems in which the effects of residual Coulomb interactions play a relevant role
Voltage drop across Josephson junctions for Lévy noise detection
Full text linkWe propose to characterize Lévy-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 Lévy 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 Lévy-distributed fluctuations. An analytical estimate of the average velocity in the case of a Lévy-driven escape process from a metastable state well agrees with the numerical calculation of the average voltage drop across the junction. The best performances are reached at small bias currents and low temperatures, i.e., when both thermally activated and quantum tunneling switching processes can be neglected. The effects discussed in this work pave the way toward an effective and reliable method to characterize Lévy components eventually present in an unknown noisy signal
Colossal orbital-Edelstein effect in non-centrosymmetric superconductors
Full text linkIn superconductors that lack inversion symmetry, the flow of supercurrent can
induce a non-vanishing magnetization, a phenomenon which is at the heart of
non-dissipative magneto-electric effects, also known as Edelstein effects. For
electrons carrying spin and orbital moments a question of fundamental relevance
deals with the orbital nature of magneto-electric effects in conventional
spin-singlet superconductors with Rashba coupling. Remarkably, we find that the
supercurrent-induced orbital magnetization is more than one order of magnitude
greater than that due to the spin, giving rise to a colossal magneto-electric
effect. The induced orbital magnetization is shown to be sign tunable, with the
sign change occurring for the Fermi level lying in proximity of avoiding
crossing points in the Brillouin zone and in the presence of superconducting
phase inhomogeneities, yielding domains with opposite orbital moment
orientation. The orbital-dominated magneto-electric phenomena, hence, have
clear-cut marks for detection both in the bulk and at the edge of the system
and are expected to be a general feature of multi-orbital superconductors
without inversion symmetry breaking.Comment: 7 pages, 5 figure
Hallmarks of non-trivial topology in Josephson junctions based on oxide nanochannels
Full text linkWe investigate the topological properties of a Josephson junction obtained by
constraining a two-dimensional electron gas at oxide interface to form a
quasi-1D conductor. We reveal an anomalous critical current behaviour with a
magnetic field applied perpendicular to the Rashba spin-orbit one. We relate
the observed critical current enhancement at small magnetic fields with a
non-trivial topology, accompanied by Majorana bound states (MBSs) pinned at the
edges of the superconducting leads. Signatures of MBSs also include a sawtooth
profile in the current-phase relation. Our findings allow to recognize
fingerprints of topological superconductivity in non-centrosymmetric materials
and confined systems with Rashba spin-orbit interaction, and to explain recent
experimental observations for which a microscopic description is still lacking.Comment: 10 pages, 8 figures, pape
Nonlinear Critical-Current Thermal Response of an Asymmetric Josephson Tunnel Junction
No full textWe theoretically investigate the critical current of a thermally biased superconductor-insulator-superconductor (S-I-S) Josephson junction formed by electrodes made from different Bardeen-Cooper-Schrieffer (BCS) superconductors. The response of the device is analyzed as a function of the asymmetry parameter, r=Tc1/Tc2. We highlight the appearance of jumps in the critical current of an asymmetric junction, namely, when r≠1. In fact, in such a case, at temperatures at which the BCS superconducting gaps coincide, the critical current suddenly increases or decreases. In particular, we thoroughly discuss the counterintuitive behavior of the critical current, which increases by enhancing the temperature of one lead, instead of monotonically reducing. In this case, we find that the largest jump of the critical current is obtained for moderate asymmetries, r≃3. In view of these results, the discussed behavior can be speculatively proposed as a temperature-based threshold single-photon detector with photon-counting capabilities, which operates nonlinearly in the nondissipative channel
ADSORPTION OF WATER MOLECULES ONTO 1:1 DIOCTAHEDRAL CLAY MINERALS: A BADER'S TOPOLOGICAL ANALYSIS OF THE AB-INITIO ELECTRON DENSITIES
No full textSolitonic thermal transport in a current-biased long Josephson junction
No full textWe investigate the coherent energy and thermal transport in a temperature-biased long Josephson tunnel junction, when a Josephson vortex, i.e., a soliton, steadily drifts driven by an electric bias current. We demonstrate that thermal transport through the junction can be controlled by the bias current, since it determines the steady-state velocity of the drifting soliton. We study the effects on thermal transport of the damping affecting the soliton dynamics. In fact, a soliton locally influences the power flowing through the junction and can cause the variation of the temperature of the device. When the soliton speed increases approaching its limiting value, i.e., the Swihart velocity, we demonstrate that the soliton-induced thermal effects significantly modify. Finally, we discuss how the appropriate material selection of the superconductors forming the junction is essential, since short quasiparticle relaxation times are required to observe fast thermal effects
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