共查询到17条相似文献,搜索用时 0 毫秒
1.
L.G. Vieira O. Hernandez A. Almeida M. Quilichini J.L. Ribeiro M.R. Chaves A. Klöpperpieper 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):447-456
We report a combined experimental study by means of elastic neutron scattering and dielectric measurements of a partially
deuterated and brominated BCCD (Betaine Calcium Chloride Dihydrate) crystal. The lowest-temperature phase is one-dimensional modulated and
characterized by the coexistence of different commensurate domains (with = 1/4, 4/17, 2/9 and 1/5 on cooling), but with a clear predominance of the five-fold phase. A huge global thermal hysteresis
of the wave-vector of the modulation, attaining values of about 9 K in the incommensurate phase and up to 15 K in the “harmless”
low temperature part of the phase diagram, is observed up to . The role of lattice defects on this phenomenon is discussed. Similarly to the behaviour of the pure compound, the structural
modulation evolves on cooling towards a soliton regime (growth of third and fifth-order satellite peaks), probably with respect
to a non-stabilized non-modulated ferroelectric phase. The critical temperatures deduced from dielectric constant and pyroelectric
current measurements are in very good agreement with those obtained from neutron scattering. The dielectric anomaly observed
in at K, and known as the “-anomaly”, could not be related with any special feature detected in the neutron data, and in particular no correlation between
this anomaly and the appearance of the soliton regime can be established.
Received 26 October 1998 相似文献
2.
C. Z. Bi J. Y. Ma J. Yan X. Fang D. Z. Yao B. R. Zhao X. G. Qiu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):167-171
Near-normal incident infrared reflectivity spectra of a
(001) YVO4 single crystal have been measured at different
temperatures in the frequency region between 100 and 6000 cm-1.
The reflectivity spectra are analyzed with the factorized form of
the dielectric function, and the dielectric properties and optical
conductivity of the YVO4 crystal are obtained. From the TO/LO
splitting, effective charges at different temperatures are
calculated to study the ionicity of YVO4. The internal modes
of the VO43- ion and the external modes of the Y(VO4) lattice
are compared with SiO44- in zircon and with other rare-earth vanadates. 相似文献
3.
H. Keiter M. Rosenberg 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):599-603
The scale of relaxation times in glasses has led to generalizations of the Drude model of the dielectric function in terms
of an integral, containing a Drude kernel and a probability distribution. This integral equation is solved by a Mellin or
a Stieltjes transform. Beyond known results, we obtain the probability distribution of the Havriliak-Negami dielectric function.
Even more general classes of dielectric models can be dealt with, using Mellin's transform. They may serve as checks for numerical
procedures applied to the underlying ill-posed problem, if experimental data for the dielectric function are used.
Received: 2 February 1998 / Accepted: 17 March 1998 相似文献
4.
J. Le Cochec F. Ladieu 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):13-26
We have calculated the real part of the nonlinear dielectric susceptibility of amorphous insulators in the kHz range, by using the two-level system model
and a nonperturbative numerical quantum approach. At low temperature T, it is first shown that the standard two-level model should lead to a decrease of when the measuring field E is raised, since raising E increases the population of the upper level and induces Rabi oscillations cancelling the ones induced from the ground level.
This predicted E-induced decrease of is at odds with experiments. However, a better, though still not perfect, agreement with low-frequency experimental nonlinear data is
recovered if, in our fully quantum simulations, interactions between defects are taken into account by a new relaxation rate
whose efficiency increases as , as was proposed recently by Burin et al. [Phys. Rev. Lett. 86, 5616 (2001)]. In this approach, the behavior of at low T is mainly explained by the efficiency of this new relaxation channel. Since a quantitative understanding of glasses is still missing, we finally discuss experiments whose results should yield a refined understanding
of this new relaxation mechanism: i) a completely new nonlinear behavior should be found for samples whose thickness is ≃
10 nm; ii) a decrease of nonequilibrium effects should be found when E is increased.
Received 19 September 2002 / Received in final form 4 December 2002 Published online 14 March 2003 相似文献
5.
M.-P. Gorza M. Ducloy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):343-356
The long-range interactions between an atomic system in an arbitrary energy
level and dispersive surfaces in thermal equilibrium at non-zero temperature
are revisited within the framework of the quantum-mechanical linear response
theory, using generalized susceptibilities for both atom and electromagnetic
field. After defining the observables of interest, one presents a general
analysis of the atomic level shift valid for any number and form of
dielectric surfaces. It is shown that, at zero temperature, one recovers
well-known results previously obtained in the linear response regime. The
case of a plane dispersive surface is elaborated on in the non-retarded
regime. Calculations are given in detail for a dielectric surface exhibiting
a single polariton resonance. Theoretical predictions are presented within a
physical viewpoint allowing one to discriminate between the various
interaction processes: on one hand, the level shift induced by non-resonant
quantum fluctuations, on the other hand, two potentially resonant
atom-surface couplings. The first resonant process appears for excited-state
atoms and originates in an atomic de-excitation channel resonantly coupled
to the surface polariton mode. It exists also at zero temperature, and has
been studied and observed previously. The second physical process, which
exists at non-zero temperature only, corresponds to the reverse process in
which a thermal quantum excitation of a surface polariton resonantly couples
to an atomic absorption channel. This novel phenomenon is predicted as well
for a ground state atom, and can turn the ordinary long-range van der Waals
attraction of atoms into a surface repulsion at increasing temperatures.
This opens the way to the control and engineering of the sign and amplitude
of van der Waals forces via surface temperature adjustment. 相似文献
6.
J. Lermé B. Palpant B. Prével E. Cottancin M. Pellarin M. Treilleux J.L. Vialle A. Perez M. Broyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):95-108
The optical response of free and matrix-embedded gold metal clusters AuN is investigated in the framework of the time-dependent local-density-approximation (TDLDA). The characteristics of the surface
plasmon resonance are carefully analyzed as a function of the model parameters and the particle radius. The strong influence
of the frequency-dependence of the 5d core-electron dielectric function in the vicinity of the interband threshold is emphasized. The size evolution of the Mie-frequency
in free gold clusters exhibits a noticeable blue-shift trend as the particle size decreases, much stronger than in silver
clusters. The width and shape of the resonance, essentially ruled by the decay via the interband transitions, are found closely correlated to the imaginary component of the core-electron dielectric function.
In presence of a surrounding matrix the blue-shift trend is largely rubbed out. Agreement with recent experimental results
on size-selected gold clusters embedded in an alumina matrix may be achieved by taking into account the porosity effects at
the metal/matrix interface. The comparison with the predictions of classical models is also provided.
Received: 9 March 1998 / Revised: 5 June 1998 / Accepted: 3 July 1998 相似文献
7.
8.
T. Dekola D. Isakov E. de Matos Gomes V. H. Nunes Rodrigues M. M.R. Costa 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(4):519-522
Glycine glycinium perrhenate is a new hydrogen bonded crystalline material that exhibits several phase transitions at low
and high temperature. At room temperature the structure shows some special features. One dimensional polar chains, linked
by strong hydrogen bonds exist parallel to [100], [010] and [–110]. The structural, thermal and dielectric properties of this
new perrhenic salt are presented and a relationship is established. 相似文献
9.
S. Giordano P. L. Palla L. Colombo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):29-35
We prove a generic theorem stating the equivalence
between a graded dielectric ellipsoid (with gradation along a family of
internal confocal ellipsoids) and an anisotropic homogeneous ellipsoid. We then describe a procedure to obtain the three principal
permittivities of the effective ellipsoid for any given dielectric gradation profile. Finally, we apply a multiscale approach
to homogenize dispersions of ellipsoidal graded particles. 相似文献
10.
J. Dec W. Kleemann Th. Woike R. Pankrath 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):627-632
The complex dielectric susceptibility of Sr
0.61
Ba
0.39
Nb
2
O
6
:Ce
3+
(SBN61:Ce) has been measured at frequencies and temperatures before and after poling. The relaxor behaviour with large polydispersivity observed above the ferroelectric phase transition
temperature, T
c
= 360 and 340 K for x
(Ce) = 0 and 0.0066, respectively, is perfectly modeled within the framework of Chamberlin's dynamically correlated domain approach.
Below T
c
the dynamic nanodomain state crosses over into a ferroelectric state with polydispersive domain wall dynamics at very low
frequencies. Presumably SBN61:Ce belongs to the three-dimensional random field Ising rather than to the dipole glass universality
class.
Received 1 October 1999 相似文献
11.
R. Eryiğit C. Parlak R. Eryiğit 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):251-254
We have performed a first-principles study of structural, dynamical, and dielectric properties of the chalcopyrite semiconductor
CuInS2. The calculations have been carried out within the local density functional approximation using norm-conserving pseudopotentials
and a plane-wave basis. Born effective charge tensors, dielectric permitivity tensors, the phonon frequencies at the Brillouin
zone center and mode oscillator strengths are calculated using density functional perturbation theory. The calculated properties
agree with infrared and Raman measurements.
Received 12 December 2002 / Received in final form 17 March 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: resul@ibu.edu.tr 相似文献
12.
An algebraic theory of dualities is developed based on the notion of bond algebras. It deals with classical and quantum dualities in a unified fashion explaining the precise connection between quantum dualities and the low temperature (strong-coupling)/high temperature (weak-coupling) dualities of classical statistical mechanics (or (Euclidean) path integrals). Its range of applications includes discrete lattice, continuum field and gauge theories. Dualities are revealed to be local, structure-preserving mappings between model-specific bond algebras that can be implemented as unitary transformations, or partial isometries if gauge symmetries are involved. This characterization permits us to search systematically for dualities and self-dualities in quantum models of arbitrary system size, dimensionality and complexity, and any classical model admitting a transfer matrix or operator representation. In particular, special dualities such as exact dimensional reduction, emergent and gauge-reducing dualities that solve gauge constraints can be easily understood in terms of mappings of bond algebras. As a new example, we show that the ?2 Higgs model is dual to the extended toric code model in any number of dimensions. Non-local transformations such as dual variables and Jordan–Wigner dictionaries are algorithmically derived from the local mappings of bond algebras. This permits us to establish a precise connection between quantum dual and classical disorder variables. Our bond-algebraic approach goes beyond the standard approach to classical dualities, and could help resolve the long-standing problem of obtaining duality transformations for lattice non-Abelian models. As an illustration, we present new dualities in any spatial dimension for the quantum Heisenberg model. Finally, we discuss various applications including location of phase boundaries, spectral behavior and, notably, we show how bond-algebraic dualities help constrain and realize fermionization in an arbitrary number of spatial dimensions. 相似文献
13.
M. Sassetti F. Napoli B. Kramer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):643-654
Using the bosonization technique, a theory for the collective excitations of the interacting electrons in quantum wires with
two subbands occupied is developed. The dispersion relations for the inter-subband charge and spin density excitations are
determined. The results are used to interpret the features observed in recent measurements of the Raman spectra of AlGaAs/GaAs
quantum wires, particularly for photon energies near band gap resonance. It is shown that peaks previously identified as “single
particle excitations” are signatures of higher order collective spin density excitations. Predictions about the observability
of the interband modes are made.
Received 8 February 1999 相似文献
14.
L. Zhang W. Kleemann J. Dec R. Wang M. Itoh 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):163-171
The dielectric permittivity ε′ - i
of SrTi 18O 3 (STO18) is studied under a dc electric field E as a function of the temperature, T. In ε′
vs.
T, a double-peak is found when 0 < E < 30 KV/m. While the peak at high-T is attributed to the smeared ferroelectric phase transition, the low-T one is induced by domain wall motion. The transverse Ising model including an external homogeneous and quenched random-fields
is successfully used to describe both the smeared phase transition and the domain wall response in the low-T domain state. The calculations are in good agreement with the experimental results.
Received 4 January 2002 / Received in final form 25 March 2002 Published online 19 July 2002 相似文献
15.
F.B. Anders M. Huth 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):491-499
We present calculations of the electronic transport properties of heavy-fermion systems within a semi-phenomenological approach
to the dynamical mean field theory. In this approach the dynamics of the Hund's rules 4f (5f )-ionic multiplet split in a crystalline environment is taken into account. Within the scope of this calculation we use the
linear response theory to reproduce qualitative features of the temperature-dependent resistivity and hall conductivity, the
magneto-resistivity and the thermoelectric power typical for heavy-fermion systems. The model calculations are directly compared
with experimental results on CeCu
2
Si
2.
Received 30 June 2000 and Received in final form 15 December 2000 相似文献
16.
E. Benichou A.R. Allouche R. Antoine M. Aubert-Frecon M. Bourgoin M. Broyer Ph. Dugourd G. Hadinger D. Rayane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(2):233-242
A non perturbative approach is used to solve the problem of a rigid linear molecule with both a permanent dipole moment and
a static dipole polarizability, in a static electric field. Eigenenergies are obtained and compared to perturbative low field
and high field approximations. Analytical expressions for the orientation parameters and for the gradient of the energy are
given. This non perturbative approach is applied to the simulation of beam deviation experiments in strong electric field.
Results of simulations are given for inhomogeneous alkali dimers. For LiNa, the simulations are compared to experimental data.
For LiK, deviation profiles have been simulated in order to prepare future experiments on this molecule.
Received 21 July 1999 and Received in final form 22 September 1999 相似文献
17.
G. Pal Y. Pavlyukh H. C. Schneider W. Hübner 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(4):483-496
A novel approach for GW-based calculations of
quasiparticle properties for finite systems is presented, in which
the screened interaction is obtained directly from a linear response
calculation of the density-density correlation function. The
conserving nature of our results is shown by explicit evaluation of
the f-sum rule. As an application, energy renormalizations and
level broadenings are calculated for the closed-shell Na9
+ and
Na21
+ clusters, as well as for Na4. Pronounced
improvements of conserving approximations to RPA-level results are
obtained. 相似文献