共查询到20条相似文献,搜索用时 31 毫秒
1.
E. Mezzetti A. Chiodoni R. Gerbaldo G. Ghigo L. Gozzelino B. Minetti C. Camerlingo C. Giannini 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):357-362
This paper reports on the striking correlation between nanosize mosaic domain walls in YBCO films and 1D rows of parallel
Josephson junctions, determining the J
c
vs.B curves. From X-ray data analysis, it results that the average “hidden" domain wall, faceted at a nanometric scale, is almost
mimicking the Josephson Junction (JJ) 1D array. The assumption that the JJs and the domain-wall arrays are coincident, enables
to find out the particular scaling field, making the J
c
vs.B curves independent of temperature. This scaling field can be interpreted in terms of the Josephson nature of the transport
current across these particular patterns in the intermediate temperature range. By means of our model it is also possible
to calculate two asymptotic behaviors of the pinning force as a function of field, for low and high fields, respectively.
These behaviors are punctually repeated by the experimental results in the same asymptotic limit, so that two corresponding
vortex regimes are clearly pointed out. All results can be interpreted by concluding that in the intermediate temperature
range, the strong pinning observed in high quality YBCO films is due to the Josephson Junctions average patterns. These patterns
are the counterpart related to the transport mechanisms of “hidden" structural nano-domains.
Received 16 October 2000 and Received in final form 28 November 2000 相似文献
2.
G.P. Pepe G. Peluso R. Scaldaferri L. Parlato C. Granata E. Esposito M. Russo 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):421-425
A new fabrication process for three-terminal superconducting devices consisting of two Josephson junctions in a stacked configuration
is reported. The process is based on the deposition of the whole Nb/AlxOy/Nb-Al/AlxOy/Nb multilayer on a Si crystalline wafer without any vacuum breaking. Lift-off techniques, anodization processes and a SiO
film deposition have been adopted for patterning and insulating the two tunnel stacked junctions. Devices have been characterized
in terms of current-voltage (I-V) curves and Josephson critical current vs. the externally applied magnetic field. They show high quality factors (V
m values up to 65 mV at 4.2 K), and good current uniformity.
Received 5 June 2001 相似文献
3.
C.H. van der Wal F.K. Wilhelm C.J.P.M. Harmans J.E. Mooij 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):111-124
We discuss the relaxation and dephasing rates that result from the control and the measurement setup itself in experiments
on Josephson persistent-current qubits. For control and measurement of the qubit state, the qubit is inductively coupled to
electromagnetic circuitry. We show how this system can be mapped on the spin-boson model, and how the spectral density of
the bosonic bath can be derived from the electromagnetic impedance that is coupled to the qubit. Part of the electromagnetic
environment is a measurement apparatus (DC-SQUID), that is permanently coupled to the single quantum system that is studied.
Since there is an obvious conflict between long coherence times and an efficient measurement scheme, the measurement process
is analyzed in detail for different measurement schemes. We show, that the coupling of the measurement apparatus to the qubit
can be controlled in situ. Parameters that can be realized in experiments today are used for a quantitative evaluation, and it is shown that the relaxation
and dephasing rates that are induced by the measurement setup can be made low enough for a time-resolved study of the quantum
dynamics of Josephson persistent-current qubits. Our results can be generalized as engineering rules for the read-out of related
qubit systems.
Received 4 September 2002 Published online 27 January 2003
RID="a"
ID="a"Present address: Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
RID="b"
ID="b"Present address: Sektion Physik and CeNS, Ludwig-Maximilians Universit?t, Theresienstr. 37, 80333 Munich, Germany e-mail: wilhelm@theorie.physik.uni-muenchen.de 相似文献
4.
E. Neumann A. Pikovsky 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):219-228
We consider the dynamics of the overdamped Josephson junction under the influence of an external quasiperiodic driving field.
In dependence on parameter values either a quasiperiodic motion or a strange nochaotic attractor (SNA) can be observed. The
latter corresponds to a resistive state in the current-voltage characteristics while for quasiperiodic motion a finite superconducting
current exists for zero voltage. It is shown that in the case of SNA a nonzero mean voltage across the junction can appear
due to symmetry breakings. Based on this observation a detailed symmetry consideration of the generalized equation of motion
is performed and symmetry conditions ensuring zero mean voltage across the junction are found.
Received 16 August 2001 and Received in final form 22 January 2002 相似文献
5.
O. Bourgeois P. Gandit J. Lesueur A. Sulpice X. Grison J. Chaussy 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(1):75-80
We report transport measurements on Superconductor/Ferromagnet/Superconductor (S/F/S) junctions: Nb/Al/Gd/Al/Nb where gadolinium
(Gd) is a weakly polarized ferromagnet. A sizeable critical current I
c is observed in the I(V) characteristics. This current can be modulated by a weak magnetic field, as expected for a Josephson current. With these
experiments, we establish that superconducting coherent transport survives across a small ferromagnetic layer. The penetration
depth of Cooper pairs in Gd has been measured. An extensive study of the Josephson critical current in temperature for different
thicknesses of magnetic compounds is presented. A comparison of transport measurements with S/N/S junction is given through
measurements made on Nb/Al/Y/Al/Nb, where yttrium (Y) is used as non magnetic rare earth metal.
Received 20 September 2000 and Received in final form 22 February 2001 相似文献
6.
R. Gerbaldo G. Ghigo G. Giunchi L. Gozzelino F. Laviano E. Mezzetti 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):297-300
We present results from an extended magneto-optical (MO) analysis of two samples cut from high-density pellets of MgB2. The first sample was studied in order to show that no matter how large the sample is and despite the bulk granularity, the
material enters into a critical state in a crystal-like fashion. The second sample was chosen for the quantitative analysis.
A numerical approach based on an inverted 2D Biot-Savart model was used to calculate the current paths across the homogeneous
polycrystalline bulk, as well as in the vicinity and across some morphological defects. Local current densities in the homogeneous
part were estimated as a function of the applied magnetic field at different temperatures, in three regimes: below full penetration,
at full penetration and above full penetration, respectively. A hypothesis of interpretation of the apparent absence of magnetic
granularity inside the polycrystalline microstructure is presented. It is related to a critical state likely reached by a
network of strongly coupled Josephson junctions.
Received 31 May 2001 and Received in final form 5 December 2001 相似文献
7.
K.H. Lee 《Solid State Communications》2011,151(12):900-903
We have studied the vortex dynamics in a ratchet array of Josephson junctions in the presence of magnetic field of 1/5 flux quantum per plaquette. The ratchet potential consists of both alternate critical currents for all the vertical junctions and alternate shunt capacitances for all the horizontal junctions. The vortices driven by an ac current in some parameters are found to show the directional motion as well as the asymmetric current-voltage characteristics. We use the time-dependent vorticity and the time-dependent vorticity-vorticity correlation function to analyze the motion of vortices on a few fractional Shapiro steps. We have found that vortices on a fractional Shapiro n/5-step move coherently through n plaquettes during a single ac cycle. The asymmetric features of the ratchet array gradually disappear as finite temperature increases. 相似文献
8.
M.P. Rekalo E. Tomasi-Gustafsson 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):575-581
The associative charm particles production in nucleon-nucleon collisions N + N↦Λc(Σc) + ˉD + N, is described in a general way and the spin and isospin structure of the corresponding matrix elements are derived. Using
an analogy with strange-particle (ΛK) production, the D-meson exchange model is considered in detail. Estimations of the energy behavior of the threshold cross-sections show a large
dependence on the form of the phenomenological hadron form factors and indicate that, at threshold, the cross-section is three
orders of magnitude smaller than for strange-particle production.
Received: 18 October 2002 / Accepted: 5 December 2002 / Published online: 18 March 2003
RID="a"
ID="a"Permanent address: National Science Center KFTI, 310108 Kharkov, Ukraine.
RID="b"
ID="b"e-mail: etomasi@cea.fr
Communicated by V.V. Anisovich 相似文献
9.
10.
The cross-sections for the reactions of muonium (anti-muonium) production in the high-energy electron (positron) scattering
by nuclei e
-(e
+) + Z↦Z + M
0(ˉM) + μ-(μ+) are calculated in dependence on energy and polarization of the initial electron (positron) and polarization of the final
μ-(μ+)-meson. Since this is a coherent phenomenon the cross-sections are proportional to Z2. For Z ∼ 100, due to the factor Z2, the cross-sections are large enough to be measured at the energies available for the HERA Collider at DESY. The results
are discussed in connection with a test of CPT invariance.
Received: 24 September 2002 / Accepted: 12 March 2003 / Published online: 27 May 2003 相似文献
11.
V. Koptev M. Nekipelov M. Büscher S. Dymov M. Hartmann V. Hejny H.R. Koch N. Lang S. Mikirtichyants H. Ohm A. Petrus Z. Rudy R. Schleichert A. Sibirtsev K. Sistemich H. Ströher K.-H. Watzlawik 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):235-240
Results of a first experiment on (K+p) and (K+d) correlations from proton-carbon (pC) and proton-deuteron (pd) interactions at beam energies above and much below the threshold for elementary kaon production in nucleon-nucleon reactions
( T
NN = 1580 MeV) are discussed. These data, obtained with the ANKE spectrometer at COSY-Jülich, provide first direct evidence
for K+ production via the two-step mechanism and an indication for a cluster mechanism. It is shown that both processes contribute
significantly in pC collisions at 1200 MeV, while they are strongly suppressed at 2300 MeV and also in pd-interactions at 1344 MeV. It is emphasized that the underlying kinematics can be exploited to distinguish between these reaction
mechanisms.
Received: 26 November 2002 / Accepted: 26 March 2003 / Published online: 20 May 2003 相似文献
12.
A. Konstadopoulou J.M. Hollingworth M. Everitt A. Vourdas T.D. Clark J.F. Ralph 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):279-285
Vortices circulating in a ring made from a Josephson array in the insulating phase are studied. The ring contains a `dual
Josephson junction' through which the vortices tunnel. External non-classical microwaves are coupled to the device. The time
evolution of this two-mode fully quantum mechanical system is studied, taking into account the dissipation in the system.
The effect of the quantum statistics of the photons on the quantum statistics of the vortices is discussed. Entropic calculations
quantify the entanglement between the two systems. Quantum phenomena in the system are also studied through Wigner functions.
After a certain time (which depends on the dissipation parameters) these quantum phenomena are destroyed due to dissipation.
Received 21 October 2002 / Received in final form 11 February 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: a.konstadopoulou@brad.ac.uk 相似文献
13.
We analyze the deviations from Maxwell-Boltzmann statistics found in recent experiments studying velocity distributions in
two-dimensional granular gases driven into a non-equilibrium stationary state by a strong vertical vibration. We show that
in its simplest version, the “stochastic thermostat” model of heated inelastic hard spheres, contrary to what has been hitherto
stated, is incompatible with the experimental data, although predicting a reminiscent high-velocity stretched-exponential
behavior with an exponent 3/2. The experimental observations lead to refine a recently proposed random restitution coefficient
model. Very good agreement is then found with experimental velocity distributions within this framework, which appears self-consistent
and further provides relevant probes to investigate the universality of the velocity statistics.
Received: 27 May 2002 / Accepted: 6 May 2003 / Published online: 27 May 2003
RID="a"
ID="a"e-mail: Alain.Barrat@th.u-psud.fr 相似文献
14.
R. Migliore A. Messina A. Napoli 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):111-115
A simple way to acquire information on the mean values of the phase operators sinϕ and cosϕ of an ultrasmall Josephson junction
prepared in an arbitrary pure or not state is reported. Our proposal exploits the recently predicted occurrence of current
spikes in the I-V characteristic of a mesojunction irradiated by a quantum single-mode low-intensity coherent electromagnetic field. A necessary
condition for the validity of our treatment is presented and discussed.
Received 11 April 2001 相似文献
15.
Zhi Ping Wang Xi Xia Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):265-271
Rayleigh-Schr?dinger perturbation theory and an improved Wigner-Brillouin perturbation theory has been used to study the cyclotron
resonance of the polarons in ternary mixed crystals in the zero-temperature limit. The interaction between an electron and
two branches of longitudinal optical phonon modes is taken into account in the framework of the random-element-isodisplacement
model. The numerical results for several ternary mixed crystals show that the polaronic cyclotron energy and mass split successively
twice related to the higher and lower branches of longitudinal optical phonon modes of ternary mixed crystals. A non-linear
dependence of the polaronic cyclotron energy and mass on the composition x is found.
Received 19 March 2002 / Received in final form 21 March 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: xxliang@imu.edu.cn 相似文献
16.
R. D'Hulst G.J. Rodgers 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(4):619-625
We present a model describing the competition between information transmission and decision making in financial markets. The
solution of this simple model is recalled, and possible variations discussed. It is shown numerically that despite its simplicity,
it can mimic a size effect comparable to a crash localized in time. Two extensions of this model are presented that allow
to simulate the demand process. One of these extensions has a coherent stable equilibrium and is self-organized, while the
other has a bistable equilibrium, with a spontaneous segregation of the population of agents. A new model is introduced to
generate a transition between those two equilibriums. We show that the coherent state is dominant up to an equal mixing of
the two extensions. We focus our attention on the microscopic structure of the investment rate, which is the main parameter
of the original model. A constant investment rate seems to be a very good approximation.
Received 7 August 2000 and Received in final form 10 September 2000 相似文献
17.
Hong-yi Fan J. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):437-442
Based on the newly constructed Einstein, Podolsky and Rosen (EPR) entangled state representation we introduce macroscopic
classical functions associated with atomic coherent state τ with angular momentum value j. These functions are proportional to the ordinary one-variable Hermite polynomials of order 2j. The corresponding Wigner quasiprobability function for τ in phase space is also derived which turns out to be a two-variable Hermite polynomial H
2j, 2j. In so doing, a new classical-quantum correspondence scheme for angular momentum system is established.
Received 7 August 2002 / Received in final form 14 December 2002 Published online 24 April 2003
RID="a"
ID="a"Work supported by the National Natural Science Foundation of China under grant 10175057.
RID="b"
ID="b"e-mail: fhym@sjtu.edu.en 相似文献
18.
A.A. Zvyagin 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):351-360
The behavior of charge and spin persistent currents in an integrable lattice ring of strongly correlated electrons with a
magnetic impurity is exactly studied. Our results manifest that the oscillations of charge and spin persistent currents are
similar to the ones, earlier obtained for integrable continuum models with a magnetic impurity. The difference is due to two
(instead of one) Fermi velocities of low-lying excitations. The form of oscillations in the ground state is “saw-tooth”-like,
generic for any multi-particle coherent one-dimensional models. The integrable magnetic impurity introduces net charge and
spin chiralities in the generic integrable lattice system, which determine the initial phase shifts of charge and spin persistent
currents. We show that the magnitude of the charge persistent current in the generic Kondo situation does not depend on the
parameters of the magnetic impurity, unlike the (magneto)resistivity of transport currents.
Received 30 January 2003 / Received in final form 12 March 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: zvyagin@fy.chalmers.se 相似文献
19.
J. Tempere S.N. Klimin I.F. Silvera J.T. Devreese 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):329-338
The properties of ripplonic polarons in a multielectron bubble in liquid helium are investigated on the basis of a path-integral
variational method. We find that the two-dimensional electron gas can form deep dimples in the helium surface, or ripplopolarons,
to solidify as a Wigner crystal. We derive the experimental conditions of temperature, pressure and number of electrons in
the bubble for this phase to be realized. This predicted state is distinct from the usual Wigner lattice of electrons: it
melts by dissociation of the ripplopolarons when the electrons shed their localizing dimple as the pressure on the multielectron
bubble drops below a critical value.
Received 20 February 2003 Published online 11 April 2003
RID="a"
ID="a"Also at: TU Eindhoven, Eindhoven, The Netherlands e-mail: devreese@uia.ua.ac.be 相似文献
20.
K. Van de Vel A.N. Andreyev R.D. Page H. Kettunen P.T. Greenlees P. Jones R. Julin S. Juutinen H. Kankaanpää A. Keenan P. Kuusiniemi M. Leino M. Muikku P. Nieminen P. Rahkila J. Uusitalo K. Eskola A. Hürstel M. Huyse Y. Le Coz M.B. Smith P. Van Duppen R. Wyss 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):167-171
Gamma rays from excited states of 190Po have been observed using the Jurosphere Ge-detector array coupled to the RITU gas-filled separator. They were associated
with a collective band which from spin 4 onwards resembles the prolate rotational bands known in the isotones 188Pb and 186Hg. This indicates that in 190Po the prolate configuration becomes yrast above I = 2. The experimental results are interpreted in a two-band mixing calculation and are in agreement with α-decay data and
potential energy surface calculations.
Received: 10 January 2003 / Accepted: 19 February 2003 / Published online: 7 May 2003 相似文献