共查询到20条相似文献,搜索用时 109 毫秒
1.
A novel dynamical state has been observed in the dynamics of a perturbed sine-Gordon system. This resonant state has been experimentally observed as a singularity in the dc current-voltage characteristic of an annular Josephson tunnel junction, excited in the presence of a magnetic field. In this respect it can be assimilated to self-resonances known as Fiske steps. Differently from these, however, we demonstrate, on the basis of numerical simulations, that its detailed dynamics involves rotating fluxon pairs, a mechanism associated, so far, to self-resonances known as zero-field steps. This occurs because the size of nonlinear excitations is comparable with that of the system. 相似文献
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We study the transport properties of a Z-shaped graphene nanoribbon (GNR). It is found that the quasibound states in the Z-shaped junction induce resonant peaks around the Dirac point in the conductance profile. The resonant transmission via the quantum bound state is very sensitive to the size of the junction. The number and also the lifetimes of the quasibound states increase with the size of the Z-shaped junction. Long lifetime bound states which do not induce obvious resonant peaks exist in the junction with a wider or longer zigzag edged GNR. The resonant characteristics of the Z-shaped GNR can be tuned by the variation of the geometrical size. 相似文献
4.
Using a quantum detector, a superconductor-insulator-superconductor junction, we probe separately the emission and absorption noise in the quantum regime of a superconducting resonant circuit at equilibrium. At low temperature the resonant circuit exhibits only absorption noise related to zero point fluctuations, whereas at higher temperature emission noise is also present. By coupling a Josephson junction, biased above the superconducting gap, to the same resonant circuit, we directly measure the noise power of quasiparticles tunneling through the junction at two resonance frequencies. It exhibits a strong frequency dependence, consistent with theoretical predictions. 相似文献
5.
The dynamics of Josephson junction equation in case of damping α>2 is investigated numerically. In this case the second-order system can be asymptotically reduced in the large to a one-dimensional circle map. We study the parametric dependence of the resonances of this system and plot the resonant regions in two-dimensional parameter space. The periodic variation of the widths of harmonic regions with increase of the periodic driving force is observed. In the limit of infinite damping, we study a first order system through suitable re-scaling and the same property is observed. We conjecture this may caused by the competition between the periodic potential and the periodic external driving in these systems. 相似文献
6.
G. Augello D. Valenti B. Spagnolo 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(2):225-234
The role of thermal and non-Gaussian noise on the dynamics
of driven short overdamped Josephson junctions is studied. The mean
escape time of the junction is investigated considering Gaussian,
Cauchy-Lorentz and Lévy-Smirnov probability distributions of the
noise signals. In these conditions we find resonant activation and
the first evidence of noise enhanced stability in a metastable
system in the presence of Lévy noise. For Cauchy-Lorentz noise
source, trapping phenomena and power law dependence on the noise
intensity are observed. 相似文献
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Zhou Tiege Mao JingCui Hanlin Zhao XinjieFang Lan Yan Shaolin 《Physica C: Superconductivity and its Applications》2009,469(13):785-788
We propose a new model of a Josephson junction array embedded in a resonant cavity. The model considers the excitation of the resonance mode by the array and the influence of the resonance mode on the array. The phase-locking properties of the junction array are investigated in the frame of the model. Resonant steps in the current–voltage characteristics due to the interaction between the array and the resonant cavity and many other features of the phase-locking behaviors have been produced. The results include the influence of the quality factor, the strength of the coupling, as well as the junction number of the array on the phase-locking properties. The model can successfully explain many features of the real situation and provide useful new predictions. 相似文献
9.
A. Föhlisch 《Applied Physics A: Materials Science & Processing》2006,85(4):351-359
In complex systems, composed from many atomic units, it is of equal importance to determine the time scales of dynamic processes and to have control at which atomic site a dynamic process was initiated. With resonant X-ray spectroscopic tools like autoionization and resonant inelastic X-ray scattering, an atomically localized excited state can be created and its dynamics monitored in comparison to the ultrafast time scale of the transient core-hole resonance. With this core-hole-clock method, charge transfer dynamics of only 320±90 attoseconds could be determined for Sulphur adsorbed on the Ru(0001) surface, extending the core-hole-clock method into the range of attoseconds. Exploiting the symmetry selection rules of resonant inelastic X-ray scattering, ultrafast atomic motion can also be investigated, which changes the molecular symmetry during a transient core-excited state. With this approach the vibrational dynamics of C2H4 on the time scale of a Carbon 1s core-hole resonance has been investigated. PACS 73.20.Jc; 32.80.Dz; 33.20.Rm; 33.20.Tp; 33.20.Fb 相似文献
10.
Yuan Ping Chen Yue E. Xie X.L. Wei L.Z. Sun JianXin Zhong 《Solid State Communications》2010,150(13-14):675-679
Three-terminal nanojunctions based on triangle zigzag edged graphene flakes are proposed and their transport properties are studied. In the solid and hollow triangle graphene junctions, there exist different resonant transmissions due to the different electronic states in the two structures. The quasi-bound states in the solid junction are confined in the inner of the triangle flake, while those in the hollow junction are confined at the zigzag edges. In addition, these states are tightly associated with the size of the triangle flake, thus the resonant transmissions in the triangle graphene junctions can be tuned by the structural size and geometry. 相似文献
11.
We investigate macroscopic dynamical quantum tunneling (MDQT) in the driven Duffing oscillator, characteristic for Josephson junction physics and nanomechanics. Under resonant conditions between stable coexisting states of such systems we calculate the tunneling rate. In macroscopic systems coupled to a heat bath, MDQT can be masked by driving-induced activation. We compare both processes, identify conditions under which tunneling can be detected with present day experimental means and suggest a protocol for its observation. 相似文献
12.
Jonas L. Svensson Patrik B.U. Andersson Wolfgang Kropp 《Journal of sound and vibration》2010,329(9):1274-1288
A theoretical investigation of wave scattering and the active modification of wave scattering at structural junctions is presented. A resonant and a non-resonant Euler-Bernoulli beam are coupled, and an external force is introduced at the junction. The external force is intended for feedforward control in order to manipulate the scattering properties at the junction. The purpose of the investigated control law is to make the junction non-reflective in the case of an incident bending wave. The control effort and the resulting power flow are investigated for different properties of the beams. By introducing damping in the resonant beam all incidence wave power is absorbed either passively, in the resonant beam, or actively, by the force. The results form the basis for a discussion of the possible benefits of using such a configuration for hybrid passive-active vibration control. The results show that for certain ratios of bending stiffness and mass the presented hybrid passive-active solution may offer advantages compared to purely passive or purely active solutions. 相似文献
13.
Summary Within the well-established quantum picture of a Josephson junction, it has been shown that the possibility of a resonant
macroscopic quantum tunnelling can produce sharp voltage peaks in the current-voltage characteristics. We investigate the
effects of the junction parametrs and bias conditions on the step amplitude, in view of an experimental check of the proposed
phenomenon. 相似文献
14.
The escape from a metastable state over an oscillating barrier of an underdamped Josephson tunnel junction has been experimentally investigated with oscillation frequency well separated from the plasma frequency of the junction. The resonant escape, namely, a minimum of the average escape time as a function of the oscillation frequency, was observed. For the oscillation frequency much smaller than the "resonant frequency," the average escape time is the average of the times required to cross over each of the barriers. On the other hand, for the oscillation frequency much greater than the "resonant frequency," the average escape time is that required to cross the average barrier. 相似文献
15.
Y. P. Chen Y. E. Xie X. H. Yan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):333-338
We have studied the transmission resonances for a confined array of
antidots, using the lattice Green's function method. Two kinds of resonant
peaks via quasibound states are found. One kind of resonant peak corresponds
to the split quasibound states. The split states originate from the
superposition of quasibound states respectively localized in different (T or
crossed) junctions, while the number of quasibound states in each junction
is associated with the arm-width of the junction. Electrons in these split
states are mainly localized in the junctions. The other kind of resonant
peaks correspond to the high quasibound states which exist in (transverse
and longitude) multi-period confined arrays of antidots. It is interesting
to note that electrons in some of the high quasibound states are mainly
localized in the intersection of the junctions rather than in the junctions
themselves. 相似文献
16.
Josephson junction is an active electric component and its channel current can be adjusted by external magnetic field, which can trigger additive phase error along the junction. From physical viewpoint, the Josephson junction can capture and release field energy when it is exposed to a magnetic field, and this time-varying current can be used to excite neural circuit for generating target firing patterns. In this paper, a Josephson junction is connected to a simple neural circuit, which is made of a capacitor, induction coil, a nonlinear resistor, two linear resistors and one constant voltage source in the branch, and the improved neural circuit is adjusted to percept external magnetic field and estimate the potential application of Josephson junction in nonlinear circuits. Bifurcation analysis is applied to explore the mode selection and dynamics dependence on parameters setting in the biophysical neural circuits. Furthermore, the neural circuit is exposed to external magnetic field and its physical effect is estimated by applying scale transformation on the variables and parameters in the neural circuit. It is confirmed that the neural circuit can be controlled and the neural activity shows distinct mode transition by taming the intensity (or angular frequency in periodic field) of external magnetic field. This kind of neural circuit can be further used as smart sensor for detecting weak magnetic field. 相似文献
17.
The transport of a walker in rocking feedback-controlled ratchets is investigated. The walker consists of two coupled “feet” that allow the interchange of the order of particles while the walker moves. In the underdamped case, the deterministic dynamics of the walker in a tilted asymmetric ratchet with an external periodic force is considered. It is found that delayed feedback ratchets with a switching-onand-off dependence of the states of the system can lead to absolute negative mobility. In such a novel phenomenon, the particles move against the bias. Moreover, the walker can acquire a series of resonant steps for different values of the current. It is interesting to find that the resonant currents of the walker are induced by the phase locked motion that corresponds to the synchronization of the motion with the change in the frequency of the external driving. These resonant steps can be well predicted in terms of time-space symmetry analysis, which is in good agreement with dynamics simulations. The transport performances can be optimized and controlled by suitably adjusting the parameters of the delayed-feedback ratchets. 相似文献
18.
Quantum interference and decoherence in single-molecule junctions is analyzed employing a nonequilibrium Green's function approach. Electrons tunneling through quasidegenerate states of a molecular junction exhibit interference effects. We show that electronic-vibrational coupling, inherent to any molecular junction, strongly quenches such interference effects. This decoherence mechanism may cause significantly larger electrical currents and is particularly pronounced if the junction is vibrationally highly excited, e.g., due to inelastic processes in the resonant transport regime. 相似文献
19.
Based on the time-convolutionless master-equation approach, we investigate the squeezing dynamics of two atoms in dissipative cavities. We find that the atomic squeezing is related to initial atomic states, atom–cavity couplings, nonMarkovian effects and resonant frequencies of an atom and its cavity. The results show that a collapse–revival phenomenon will occur in the atomic squeezing and this process is accompanied by the buildup and decay of entanglement between two atoms. Enhancing the atom–cavity coupling can increase the frequency of the collapse–revival of the atomic squeezing.The stronger the non-Markovian effect is, the more obvious the collapse–revival phenomenon is. In particular, if the atom–cavity coupling or the non-Markovian effect is very strong, the atomic squeezing will tend to a stably periodic oscillation in a long time. The oscillatory frequency of the atomic squeezing is dependent on the resonant frequency of the atom and its cavity. 相似文献
20.
《中国物理快报》2016,(11)
We consider a superconducting(Josephson) junction driven by the thermal noise with an ac drive current and a dc constant bias current in the overdamped case and in the underdamped case,respectively,and investigate the effect of the constant bias current on the evolution of the net voltage versus the driving frequency.It is shown that,with some suitably selected values of the system's parameters,suitably increasing the absolute value of the constant bias current can lead to the enhancement of resonant activation of the net voltage versus the driving frequency.This result can benefit the investigation for the Josephson junction subjected to the constant bias current(or voltage). 相似文献