共查询到20条相似文献,搜索用时 15 毫秒
1.
T. Grenet J. Delahaye M. Sabra F. Gay 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):183-197
We present a study of non-equilibrium phenomena observed
in the electrical conductance of insulating granular aluminium thin films.
An anomalous field effect and its slow relaxation are studied in some
detail. The phenomenology is very similar to the one already observed in
indium oxide. The origin of the phenomena is discussed. In granular systems,
the present experiments can naturally be interpreted along two different
lines. One relies on a slow polarisation in the dielectric surrounding the
metallic islands. The other one relies on a purely electronic mechanism: the
formation of an electron Coulomb glass in the granular metal. More selective
experiments and/or quantitative predictions about the Coulomb glass
properties are still needed to definitely distinguish between the two
scenarios. 相似文献
2.
J. Delahaye T. Grenet F. Gay 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(1):5-19
We perform electrical field effect measurements at 4 K on insulating granular aluminium thin films. When the samples size
is reduced below ≃100 μm, reproducible and stable conductance fluctuations are seen as a function of the gate voltage. Our results suggest that these
fluctuations reflect the incomplete self-averaging of largely distributed microscopic resistances. We also study the anomalous
field effect (conductance dip) already known to exist in large samples and its slow relaxation in the presence of the conductance
fluctuations. Within our measurements accuracy, the two phenomena appear to be independent of each other, like two additive
contributions to the conductance. We discuss the possible physical meaning of this independence and in particular whether
or not this observation is in favor of an electron glass interpretation of slow conductance anomaly relaxations. 相似文献
3.
G. Michałek B.R. Bułka 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):121-128
The currents and their fluctuations in two capacitively coupled single electron transistors are determined in the limit of
sequential tunnelling. Our considerations are restricted to the case when the islands (dots) of the transistors are atomic-sized,
which means each of them has only one single electronic level available for the tunnelling processes. The Coulomb interactions
of accumulated charges on the both single electron transistors lead to the effect of the negative differential resistance.
An enhancement of the current shot-noise was also found. Spectral decomposition analysis indicated the two main contributions
to the shot-noise: low- and high-frequency fluctuations. It was found that the low frequency fluctuations (polarization noise)
are responsible for a strong enhancement of the current noise.
Received 9 October 2001 / Received in final form 8 March 2002 Published online 9 July 2002 相似文献
4.
M. Specht M. Sanquer S. Deleonibus G. Guégan 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):503-508
We report observation of the Kondo effect in the Coulomb blockade oscillations of an impurity quantum dot (IQD). This IQD
is formed in the channel of a 100 nm gate length Silicon MOSFET. The quantitative analysis of the anomalous temperature and
voltage dependence for the drain-source current over a series of Coulomb blockade oscillations is performed. It strongly supports
the Kondo explanation for the conductance behavior at very low temperature in this standard microelectronics device.
Received 13 November 2001 and Received in final form 18 February 2002 相似文献
5.
Y.C. Tao X.F. Jiang J. Wang D.Y. Xing 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):463-469
An extended tunneling Hamiltonian method is proposed to study the temperature-dependent tunneling magnetoresistance (TMR)
in doped magnetic tunnel junctions. It is found that for nonmagnetic dopants (Si), impurity-assisted tunneling is mainly elastic,
giving rise to a weak spin polarization, thereby reduces the overall TMR, while for magnetic ions (Ni), the collective excitation
of local spins in δ-doped magnetic layer contributes to the severe drop of TMR and the behavior of the variation of TMR with
temperature different from that for Si-doping. The theoretical results can reproduce the main characteristic features of experiments.
Received 13 January 2002 / Received in final form 30 November 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: yctao12@163.com 相似文献
6.
Zhenhong Dai Jinzuo Sun Lide Zhang Maowang Lu Zuohong Li Shiyong Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):141-145
Artificial molecules, namely laterally coupled quantum dots with a three-dimensional spherical confinement potential well
of radius R and depth V
0, were studied by the unrestricted Hartree-Fock-Roothaan (UHFR) method. By varying the distance d between the centers of the two coupled quantum dots, the transition from the strong coupling situation to the weak one is
realized. Hund's rule, suitable for a single quantum dot is destroyed in certain conditions in the artificial molecule. For
example, in the few-electron system of the strongly coupled quantum-dot molecule, a transformation of spin configuration has
been found.
Received 8 March 2002 / Received in final form 29 May 2002 Published online 17 September 2002 相似文献
7.
8.
G. Göppert H. Grabert 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):687-704
We study the linear conductance of single electron devices showing Coulomb blockade phenomena. Our approach is based on a
formally exact path integral representation describing electron tunneling nonperturbatively. The electromagnetic environment
of the device is treated in terms of the Caldeira-Leggett model. We obtain the linear conductance from the Kubo formula leading
to a formally exact expression which is evaluated in the semiclassical limit. Specifically we consider three models. First,
the influence of an electromagnetic environment of arbitrary impedance on a single tunnel junction is studied focusing on
the limits of large tunneling conductance and high to moderately low temperatures. The predictions are compared with recent
experimental data. Second, the conductance of an array of N tunnel junctions is determined in dependence on the length N of the array and the environmental impedance. Finally, we consider a single electron transistor and compare our results for
large tunneling conductance with experimental findings.
Received 2 February 2000 相似文献
9.
P. Doussineau A. Levelut 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):13-21
Aging, memories after temperature sweeps (double ramp and double jump) and memories after electric field sweeps (double ramp
and double jump) were studied as a function of frequency. The experiments were performed at low temperatures in the ferroelectric
phase of two potassium niobo-tantalate crystals K Ta1-xNbxO3 with the niobium concentration x close to 0.02. Five complex quantities are defined, which respectively characterize these five phenomena. The main feature
is that isothermal aging and memories after temperature sweeps have exactly the same frequency dependence while after electric
field sweeps the frequency dependence is clearly different. Additionally, the role of the characteristics of the sweeps (amplitudes,
rates of changes, durations) on these memories were measured. The observed behaviours are discussed in term of a model which
attributes the time dependent effects to growth and reconformation of ferroelectric domains and takes into account that the
domain wall motion is hindered by pinning sites. The difference in the frequency dependences against the nature of the swept
parameters shows that the distribution of the reconformation time is sensitive to the biasing electric field.
Received 28 May 2001 and Received in final form 10 October 2001 相似文献
10.
The Coherent Potential Approximation (CPA) self-consistent equation is calculated for a binary disordered chain introducing
a simple transformation. The transformation reduces the CPA equation to a cubic polynomial whose complex roots are related
to the Green function and their relation to the complex Lyapunov exponent is also established. This solution fruitfully captures
essential aspects of the well-known anomalous scaling behaviors in a different and advantageous way. It is found that the
anomalous behavior is strongly effected by the nature of these roots. A small disorder expansion is carried out for comparison
with the previous weak disorder calculations. We found that the CPA reproduced the anomalous behavior of the exact calculations.
Received 22 April 2002 Published online 1st October 2002
RID="a"
ID="a"e-mail: avgin@bornova.ege.edu.tr 相似文献
11.
Zheng-Chuan Wang Qing-Rong Zheng Gang Su Bao-Heng Zhao 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):589-597
In this paper, we apply Büttiker's gauge invariant, charge conservation, nonlinear transport theory to explore the spin-polarized
tunneling of ferromagnet/insulator (semiconductor) single and double junctions. The Green function of spin-polarized tunneling
is calculated by the tight-binding approximation method. The energy and the angle (between the molecular field and the vertical
axis) dependences of the weakly nonlinear dc transport coefficient and the linear low frequency ac transport coefficient are
investigated. The ac tunneling magnetoresistance is also discussed.
Received 1st September 2000 and Received in final form 5 December 2000 相似文献
12.
R. Baltin Y. Gefen G. Hackenbroich H.A. Weidenmüller 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):119-129
We investigate the Coulomb blockade resonances and the phase of the transmission amplitude of a deformed ballistic quantum
dot weakly coupled to leads. We show that preferred single-particle levels exist which stay close to the Fermi energy for
a wide range of values of the gate voltage. These states give rise to sequences of Coulomb blockade resonances with correlated
peak heights and transmission phases. The correlation of the peak heights becomes stronger with increasing temperature. The
phase of the transmission amplitude shows lapses by between the resonances. Implications for recent experiments on ballistic quantum dots are discussed.
Received 17 July 1998 相似文献
13.
In this paper we consider the movement of an electron in the single electron tunnel process through a mesoscopic capacitor. The results show that, due to the Coulomb force, there is a threshold voltage Vt in the mesoscopic LC circuit. When the external voltage is lower than the threshold voltage, the tunnel current value is zero, and the Coulomb blockade phenomenon arises. Furthermore, considering that the mesoscopic dimension is comparable to the coherence length in which charge carriers retain the phase remembrance, a weak coupling can be produced through the proximity effect of the normal metal electrons of both electrodes of a mesoscopic capacitor. By varying the external voltage, we can observe the Shapiro current step on the current-voltage characteristic curve of a mesoscopic LC circuit. 相似文献
14.
P. Doussineau T. de Lacerda-Arôso A. Levelut 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):455-462
Slow dynamics has been studied in various potassium niobo-tantalate crystals (KTN) by recording the complex dielectric constant
after several thermal histories: isothermal evolution following controlled cooling or rapid quenching, positive or negative
temperature cycles. The results reveal most of the behaviours of aging already found in lithium-potassium tantalate (KLT):
effective ergodicity breaking (the asymptotic value of the dielectric constant varies as the logarithm of the cooling rate
R), quasi-independence of the isothermal evolution with respect to a sojourn at lower temperature. But some differences between
KTN and KLT are noticeable: coefficients of with opposite signs, role of the quenching temperature on the subsequent evolution, no overshot after a temperature jump.
In order to explain the results we propose to extend the model initially developped for KLT taking into account the different
nature of the low temperature phase, paraelectric for KLT and ferroelectric for KTN. In this model the variations of the dielectric
constant are attributed to the slow movements of polarization domain walls hindered by static random fields. By measuring
the dielectric constant during cooling and immediate heating at the same rate, an illustrative comparison is provided, showing
that the evolution of the domain size is reversible in KLT and not in KTN.
Received 17 November 1999 相似文献
15.
J.E.S. Socolar D.G. Schaeffer P. Claudin 《The European physical journal. E, Soft matter》2002,7(4):353-370
A theory of stress fields in two-dimensional granular materials based on directed force chain networks is presented. A general
Boltzmann equation for the densities of force chains in different directions is proposed and a complete solution is obtained
for a special case in which chains lie along a discrete set of directions. The analysis and results demonstrate the necessity
of including nonlinear terms in the Boltzmann equation. A line of nontrivial fixed-point solutions is shown to govern the
properties of large systems. In the vicinity of a generic fixed point, the response to a localized load shows a crossover
from a single, centered peak at intermediate depths to two propagating peaks at large depths that broaden diffusively.
Received 16 January 2002 相似文献
16.
We investigate stationary and travelling wave solutions of the classical one-dimensional transverse field Ising model. Results
are given on the existence, shape and stability of kink solutions and periodic solutions. We review recent analytical results
(e.g., the proof of existence of a one-parameter family of stationary kink solutions and the proof of existence of travelling wave
kink solutions with nonzero velocity c≠ 0) and extend them by the use of numerical methods. Small oscillations arising in the tails of travelling kink solutions
are investigated numerically. In the end, stability analysis puts some light on pinning effects.
Received 23 February 2001 and Received in final form 4 October 2001 相似文献
17.
D.A. Head A.V. Tkachenko T.A. Witten 《The European physical journal. E, Soft matter》2001,6(1):99-105
By employing the adaptive network simulation method, we demonstrate that the ensemble-averaged stress caused by a local force
for packings of frictionless rigid beads is concentrated along rays whose slope is consistent with unity: forces propagate
along lines at 45 degrees to the horizontal or vertical. This slope is shown to be independent of polydispersity or the degree
to which the system is sheared. Further confirmation of this result comes from fitting the components of the stress tensor
to the null stress “constitutive equation”. The magnitude of the response is also shown to fall off with the -1/2 power of
distance. We argue that our findings are a natural consequence of a system that preserves its volume under small perturbations.
Received 30 April 2001 and Received in final form 16 August 2001 相似文献
18.
D. Serero G. Reydellet P. Claudin É. Clément D. Levine 《The European physical journal. E, Soft matter》2001,6(2):169-179
We measured the vertical pressure response function of a layer of sand submitted to a localized normal force at its surface.
We found that this response profile depends on the way the layer has been prepared: all profiles show a single centered peak
whose width scales with the thickness of the layer, but a dense packing gives a wider peak than a loose one. We calculate
the prediction of isotropic elastic theory in the presence of a bottom boundary and compare it to the data. We found that
the theory gives the right scaling and the correct qualitative shape, but fails to really fit the data.
Received 3 August 2001 相似文献
19.
W. Peng P.M. Goldbart 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):461-466
Certain density correlators, measurable via various experimental techniques, are studied in the context of the vulcanization transition. It is shown that these correlators
contain essential information about both the vulcanization transition and the emergent amorphous solid state. Contact is made
with various physical ingredients that have featured in experimental studies of amorphous colloidal and gel systems and in
theoretical studies of the glassy state.
Received 30 September 2000 相似文献
20.
F. Zontone F. D'Acapito G. Faraci A.R. Pennisi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):501-505
We report on the formation and detection of a compressed fluid phase of Xe clusters in as- implanted Si, at room temperature.
The simultaneous structural characterization of the Xe clusters and of the Si matrix was performed by X-ray diffraction at
grazing incidence coupled with two-dimensional detection; in both cases, the nearest-neighbor distance and the coordination
were obtained. In order to investigate the early stage of the atomic inclusion and the cluster segregation, the average compression
and size of Xe fluid clusters within the amorphous Si matrix were explained within the simple Hard Sphere model.
Received 4 September 2000 and Received in final form 13 December 2000 相似文献