共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Giroud K. Hasselbach H. Courtois D. Mailly B. Pannetier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):103-109
We present electrical transport experiments performed on submicron hybrid devices made of a ferromagnetic conductor (Co) and
a superconducting (Al) electrode. The sample was patterned in order to separate the contributions of the Co conductor and
of the Co-Al interface. We observed a strong influence of the Al electrode superconductivity on the resistance of the Co conductor.
This effect is large only when the interface is highly transparent. We characterized the dependence of the observed resistance
decrease on temperature, bias current and magnetic field. As the differential resistance of the ferromagnet exhibits a non-trivial
asymmetry, we claim that the magnetic domain structure plays an important role in the electron transport properties of superconducting
/ ferromagnetic conductors.
Received 9 July 2002 / Received in final form 22 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: herve.courtois@grenoble.cnrs.fr
RID="b"
ID="b"associated to Université Joseph Fourier 相似文献
2.
M. Krawiec B.L. Györffy J.F. Annett 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):163-176
We study the ground state properties of a superconductor-ferromagnet-insulator trilayer on the basis of a Hubbard Model featuring
exchange splitting in the ferromagnet and electron-electron attraction in the superconductor. We solve the spin-polarized
Hartree-Fock-Gorkov equations together with the Maxwell's equation (Ampere's law) fully self-consistently with respect to
the order parameter and the current. For certain values of the exchange splitting we find that a spontaneous spin polarized
current is generated in the ground state and is intimately related to Andreev bound states at the Fermi level. Moreover, the
polarization of the current strongly depends on the band filling.
Received 23 September 2002 / Received in final form 13 December 2002 Published online 1st April 2003
RID="a"
ID="a"e-mail: m.a.krawiec@bristol.ac.uk 相似文献
3.
L. Yang J. Chen H. Yang J. Dong 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):215-219
We have constructed four types single-wall carbon nanotube intramolecular junctions (IMJs) of (5,5)/(8,0), (5,5)/(10,0), (5,5)/(9,0)A, and (5,5)/(9,0)B along a common axis, and calculated their electronic and transport properties using a tight binding-based Green's function
approach that is particular suitable for realistic calculation of electronic transport property in extended system. Our results
show that quasi-localized states can appear in the metal/semiconductor heterojunctions ((5,5)/(8,0) and (5,5)/(10,0)junctions),
which is desirable for the design of a quantum device; and the conductance of M-M IMJs is very sensitive to the connectivity
of the matching tubes, certain configurations of connection completely stop the flow of electron, while others permit the
transmission of the current through the interface. These results may have implications for the device assembly and manipulation
process of all carbon nanotubes-based microelectronic elements.
Received 14 January 2003 / Received in final form 25 February 2003 Published online 4 June 2003
RID="a"
ID="a"e-mail: lfyzz@yahoo.com.cn 相似文献
4.
H. Behringer M. Pleimling A. Hüller 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):81-93
Cluster molecular field approximations represent a substantial progress over the simple Weiss theory where only one spin is
considered in the molecular field resulting from all the other spins. In this work we discuss a systematic way of improving
the molecular field approximation by inserting spin clusters of variable sizes into a homogeneously magnetised background.
The density of states of these spin clusters is then computed exactly. We show that the true non-classical critical exponents
can be extracted from spin clusters treated in such a manner. For this purpose a molecular field finite size scaling theory
is discussed and effective critical exponents are analysed. Reliable values of critical quantities of various Ising and Potts
models are extracted from very small system sizes.
Received 30 September 2002 / Received in final form 25 November 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: pleim@theorie1.physik.uni-erlangen.de 相似文献
5.
B. Eckhardt R. Pandit 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):373-378
We consider the effects of a shear on velocity fluctuations in a flow. The shear gives rise to a transient amplification that
not only influences the amplitude of perturbations but also their time correlations. We show that, in the presence of white
noise, time correlations of transversal velocity components are exponential and that correlations of the longitudinal components
are exponential with an algebraic prefactor. Cross correlations between transversal and downstream components are strongly
asymmetric and provide a clear indication of non-normal amplification. We suggest experimental tests of our predictions.
Received 26 February 2002 / Received in final form 11 March 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: bruno.eckhardt@physik.uni-marburg.de
RID="b"
ID="b"Also at: Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India 相似文献
6.
I. Lubashevsky P. Wagner R. Mahnke 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):243-247
This paper introduces a car following model where the driving scheme takes into account the deficiencies of human decision
making in a general way. Additionally, it improves certain shortcomings of most of the models currently in use: it is stochastic
but has a continuous acceleration. This is achieved at the cost of formulating the model in terms of the time derivative of
the acceleration, making it non-Newtonian. However, the recipe for construction of bounded rational driver models proposed
in this paper seems to be very general and can be applied to most, if not all of the traditional car-following models.
Received 18 November 2002 / Received in final form 6 February 2003 Published online 1st April 2003
RID="a"
ID="a"e-mail: ialub@fpl.gpi.ru
RID="b"
ID="b"e-mail: peter.wagner@dlr.de
RID="c"
ID="c"e-mail: reinhard.mahnke@physik.uni-rostock.de 相似文献
7.
N.A. Taylanov G.R. Berdiyorov 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):343-348
The problem of the thermal and magnetic destruction of the critical state in composite superconductors is investigated. The
initial distributions of temperature and electromagnetic field are assumed to be essentially inhomogeneous. The limit of the
thermomagnetic instability in quasi-stationary approximation is determined. The obtained integral criterion, unlike the analogous
criterion for a homogeneous temperature profile, is shown to take into account the influence of any part of the superconductor
on the threshold for critical-state instability.
Received 11 October 2001 / Received in final form 30 November 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: taylanov@iaph.tkt.uz 相似文献
8.
S.A. Blundell M.D. Núñez-Regueiro 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):453-456
From the recently determined structure of the delafossite YCuO2.5, we argue that the Cu-O network has nearly independent Δ chains but with different interactions between the s = 1/2 spins. Motivated by this observation, we study the Δ chain for different ratios of the base-base and base-vertex interactions,
J
bb/J
bv. By exact diagonalization and extrapolation, we show that the elementary excitation spectrum is the same for total spins
S
tot = 0 and 1, but not for S
tot = 2, and has a gap only in the interval 0.4874(1) ⩽ J
bb/J
bv ⩽ 1.53(1). The gap, known to be dispersionless for J
bb = J
bv, is found to acquire increasing k-dependence as J
bb/J
bv moves away from unity.
Received 29 October 2002 / Received in final form 14 January 2003 Published online 6 March 2003
RID="a"
ID="a"e-mail: sblundell@cea.fr
RID="b"
ID="b"e-mail: nunezreg@lps.u-psud.fr 相似文献
9.
M. Camarda G.G.N. Angilella R. Pucci F. Siringo 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):273-277
The Gaussian Effective Potential in a fixed transverse unitarity gauge is studied for the static three-dimensional U(1) scalar
electrodynamics (Ginzburg-Landau phenomenological theory of superconductivity). In the broken-symmetry phase the mass of the
electromagnetic field (inverse penetration depth) and the mass of the scalar field (inverse correlation length) are both determined
by solution of the coupled variational equations. At variance with previous calculations, the choice of a fixed unitarity
gauge prevents from the occurrence of any unphysical degree of freedom. The theory provides a nice interpolation of the experimental
data when approaching the critical region, where the standard mean-field method is doomed to failure.
Received 18 November 2002 / Received in final form 26 March 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: giuseppe.angilella@ct.infn.it 相似文献
10.
G. Stenuit S. Michotte J. Govaerts L. Piraux 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(1):103-107
Theoretical and experimental magnetizations of lead nanowire arrays well below the superconducting transition temperature
Tc are described. The magnetic response of the array was investigated with a SQUID magnetometer. Hysteretic behaviour and phase
transitions have been observed in sweeping up and down the external magnetic field at different temperatures. The Meissner
and Abrikosov states were also experimentally observed in this apparently type-I superconductor. This fact brings to the fore
the non-trivial behaviour of the critical boundary κ
c ( = 1/ in bulk materials) between type-I and type-II phase transitions at mesoscopic scales. The time-independent Ginzburg-Landau
equations particularized to cylindrically symmetric configurations enable one to explain and reproduce the experimental magnetization
curves within 10% of error.
Received 16 January 2003 / Received in final form 27 March 2003 Published online 23 May 2003
RID="a"
ID="a"e-mail: stenuit@fynu.ucl.ac.be 相似文献
11.
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
12.
L. Pareti M. Solzi F. Albertini A. Paoluzi 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):303-307
We have studied the isothermal entropy change around a first-order structural transformation and in correspondence to the
second-order Curie transition in the ferromagnetic Heusler alloy Ni2.15Mn0.85Ga. The results have been compared with those obtained for the composition Ni2.19Mn0.81Ga, in which the martensitic structural transformation and the magnetic transition occur simultaneously. With a magnetic field
span from 0 to 1.6 T, the magnetic entropy change reaches the value of 20 J/kg K when transitions are co-occurring, while
5 J/kg K is found when the only structural transition occurs.
Received 27 September 2002 / Received in final form 17 February 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: solzi@fis.unipr.it 相似文献
13.
B.H. Wu J.C. Cao G.Q. Xia H.C. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(1):9-14
A detailed calculation of interface phonon assisted electron intersubband transition in double GaAs/AlGaAs quantum well structure
is presented. Our calculation concentrates on the lowest two subbands which can be designed to be in resonance with a given
interface phonon mode. Various phonon mode profiles display quasi-symmetric or quasi-antisymmetric shapes. The quasi-antisymmetric
phonon modes give rise to much larger transition rates than those assisted by quasi-symmetric ones. The transition rate reaches
a maximum when the subband separation coincides with a given phonon mode energy. The calculation procedure presented here
can be easily applied to the design and simulation of other low dimensional semiconductor structures, such as quantum cascade
lasers.
Received 22 December 2002 Published online 23 May 2003
RID="a"
ID="a"e-mail: bhwu@263.net 相似文献
14.
The segmental ordering within a lamellar polystyrene-polydimethylsiloxane diblock (PS-PDMS) was examined by NMR. A non-uniform
stretching of the PDMS chains was evidenced. Although chain segments displaying isotropic reorientational motions are present
along the chains, relaxation measurements on the free PDMS extremities demonstrate that these latter are oriented and submitted
to a non-zero constraint. This specific result allows to precise some features of the order distribution within the lamellae.
Received: 27 March 2003 / Accepted: 9 May 2003 / Published online: 4 June 2003
RID="a"
ID="a"e-mail: deloche@lps.u-psud.fr 相似文献
15.
G. De Smedt C. Godrèche J.M. Luck 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):215-225
We consider a ferromagnetic Ising chain evolving under Kawasaki dynamics at zero temperature. We investigate the statistics
of the blocking time, as well as various characteristics of the metastable configurations reached by the system, including
the statistics of the final energy, the spin correlations, and the distribution of domain sizes. Results of extensive numerical
simulations are compared with analytical predictions made for the a priori ensemble of all blocked configurations with equal weights. Qualitative differences are found, e.g. in the domain sizes, which are found to be neither statistically independent nor exponentially distributed.
Received 24 October 2002 / Received in final form 13 January 2003 Published online 1st April 2003
RID="a"
ID="a"e-mail: luck@spht.saclay.cea.fr
RID="b"
ID="b"URA 2306 of CNRS 相似文献
16.
Large spin systems as given by magnetic macromolecules or two-dimensional spin arrays rule out an exact diagonalization of
the Hamiltonian. Nevertheless, it is possible to derive upper and lower bounds of the minimal energies, i.e. the smallest energies for a given total spin S. The energy bounds are derived under additional assumptions on the topology of the coupling between the spins. The upper
bound follows from “n-cyclicity", which roughly means that the graph of interactions can be wrapped round a ring with n vertices. The lower bound improves earlier results and follows from “n-homogeneity", i.e. from the assumption that the set of spins can be decomposed into n subsets where the interactions inside and between spins of different subsets fulfill certain homogeneity conditions. Many
Heisenberg spin systems comply with both concepts such that both bounds are available. By investigating small systems which
can be numerically diagonalized we find that the upper bounds are considerably closer to the true minimal energies than the
lower ones.
Received 22 October 2002 / Received in final form 4 April 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: jschnack@uos.de 相似文献
17.
Castelnovo M Bowles RK Reiss H Gelbart WM 《The European physical journal. E, Soft matter》2003,10(2):191-197
We consider the problem of inserting a stiff chain into a colloidal suspension of particles that interact with it through
excluded volume forces. The free energy of insertion is associated with the work of creating a cavity devoid of colloid and
sufficiently large to accommodate the chain. The corresponding work per unit length is the force that resists the entry of
the chain into the colloidal suspension. In the case of a hard sphere fluid, this work can be calculated straightforwardly
within the scaled particle theory; for solutions of flexible polymers, on the other hand, we employ simple scaling arguments.
The forces computed in these ways are shown, for nanometer chain and colloid diameters, to be of the order of tens of pN for solution volume fractions of a few tenths. These magnitudes are argued to be important for biophysical processes such
as the ejection of DNA from viral capsids into the cell cytoplasm.
Received 18 December 2002 Published online: 16 April 2003
RID="a"
ID="a"e-mail: castel@chem.ucla.edu
RID="b"
ID="b"Present address: Courant Institute of Mathematical Sciences, NYU, New York, New York 10012, USA 相似文献
18.
The influence of a weight-dependent spike-timing dependent plasticity (STDP) rule on the temporal evolution and equilibrium
state of a certain synapse is investigated. We show that under certain conditions, a spike-induced rate-learning scheme could
be achieved. Through studying the situation when a single Hodgkin-Huxley neuron is driven by a large ensemble of input neurons,
we find that synchronized firing of a sub population of input neurons may be important to information processing in the nervous
system. Using simulations, we show that the temporal structure of the spike trains of these synchronized input neurons can
be transmitted reliably; further, synapses from these neurons will increase stably due to the STDP rule and this may provide
a mechanism for learning and information storage in biologically plausible network models.
Received 12 September 2002 / Received in final form 12 December 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: huang_yue@netease.com 相似文献
19.
M. Modarres H.R. Moshfegh A. Sepahvand 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(2):159-166
The free energy of the homogeneous electron fluid at finite temperature is obtained using the lowest order constrained variational
(LOCV) method. In order to test the convergence of cluster expansion series the three-body cluster terms are calculated with
the LOCV correlation functions. The results agree reasonably with those of Monte Carlo, coupled-cluster, perturbational expansion
etc, techniques at zero temperature. The flashing and critical temperatures as well as the critical exponent are found to
be about 0.6, 1.3 eV and 0.384 respectively. A similar liquid-gas phase transition to that of nuclear matter and liquid He3 is observed.
Received 15 April 2002 / Received in final form 19 October 2002 Published online 4 February 2003
RID="a"
ID="a"e-mail: modarres@khayam.ut.ac.ir 相似文献
20.
A new and general approach is proposed to analyze the dynamics of a colloidal particle interacting with a nearby wall. This
analysis can be used to determine the acting forces even when the system is non-stationary. As an illustration, we use total
internal reflection microscopy to investigate the forces acting on a polystyrene sulfate latex particle as it is receding
from a charged glass surface.
Received 10 October 2002 Published online: 16 April 2003
RID="a"
ID="a"Present address: Department of Polymer Physics, BASF Aktiengesellschaft, 67056 Ludwigshafen, Germany
RID="b"
ID="b"Present address: Arryx. Inc., Chicago, IL 60601, USA 相似文献