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1.
In this paper, we discuss the equilibrium phases and collapse transitions of a lyotropic nematic gel immersed in an isotropic
solvent. A nematic gel consists of a cross-linked polymer network with rod-like molecules embedded in it. Upon decreasing
the quality of the solvent, we find that a lyotropic nematic gel undergoes a discontinuous volume change accompanied by an
isotropic-nematic transition. We also present phase diagrams that these systems may exhibit. In particular, we show that coexistence
of two isotropic phases, of two nematic phases, or of an isotropic and a nematic phase can occur.
Received 15 February 2002 and Received in final form 14 June 2002 相似文献
2.
V.V. Savkin A.N. Rubtsov T. Janssen 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):525-531
The classical two-dimensional discrete frustrated φ
4
model is studied by Monte Carlo simulations. The correlation function is obtained for two values of a parameter d that determines the frustration in the model. The ground state is a ferro-phase for d
= - 0.35 and a commensurate phase with period N
= 6 for d
= - 0.45. Mean field predicts that at higher temperature the system enters a para-phase via an incommensurate state, in both cases. Monte Carlo data for d
= - 0.45 show two phase transitions with a floating-incommensurate phase between them. The phase transition at higher temperature
is of the Kosterlitz-Thouless type. Analysis of the data for d
= - 0.35 shows only a single phase transition between the floating-fluid phase and the ferro-phase within the numerical error.
Received 16 December 2002 / Received in final form 17 January 2003 Published online 6 March 2003
RID="a"
ID="a"e-mail: vladimir@shg.ru 相似文献
3.
R. Lefort A. Hédoux Y. Guinet E. Cochin M. Descamps 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):519-525
The first analysis of rapid intramolecular motions of triphenyl phosphite by 2H NMR is presented. The fragile slowing down of the primary relaxation is followed by a solid-echo method. The occurrence
of a fast reorientation of the phenyl side groups is demonstrated in the supercooled liquid state, identified as a two-fold
flip on the basis of simple lineshape simulations. Coexistence of both static and motionally averaged components in “two phase”
spectra indicate a broad distribution of correlation times for this relaxation. This dynamical behavior is shown to persist
in the glacial phase.
Received 28 May 2002 / Received in final form 1st October 2002
Published online 31 December 2002 相似文献
4.
Q.S. Hu H. Zheng 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):255-262
A new perturbation approach is developed for single- and many-electron Holstein model in one-, two-, and three-dimension.
The results show that this approach has a good agreement with the Migdal theory in the adiabatic regime when the coupling
is moderate (λ < 1), but with the Lang-Firsov theory in the antiadiabatic regime ( ω/W≫ 1). In the intermediate region, our approach can describe the transition from a large-polaron Fermi-liquid to the small-polaron,
and this transition may be discontinuous in adiabatic regime, which means a phase transition appears in many-electron system.
In single-electron case, we eliminate the abrupt transition using the degenerate perturbation theory, and the calculated ground
state energy and effective mass are successfully compared with those of previous authors. Besides, the method has the advantage
of requiring little computational effort.
Received 27 December 2001 / Received in final form 8 April 2002 Published online 31 July 2002 相似文献
5.
R. Zitzler Th. Pruschke R. Bulla 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):473-481
We discuss the ground state magnetic phase diagram of the Hubbard model off half filling within the dynamical mean-field theory.
The effective single-impurity Anderson model is solved by Wilson's numerical renormalization group calculations, adapted to
symmetry broken phases. We find a phase separated, antiferromagnetic state up to a critical doping for small and intermediate
values of U, but could not stabilize a Néel state for large U and finite doping. At very large U, the phase diagram exhibits an island with a ferromagnetic ground state. Spectral properties in the ordered phases are discussed.
Received 9 January 2002 Published online 25 June 2002 相似文献
6.
E. Buixaderas V. Porokhonskyy A. Paskhin M. Savinov J. Petzelt 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):319-329
Barium sodium niobate (BNN) single crystals are studied by IR spectroscopy, time-domain THz transmission spectroscopy, HF
coaxial wave-guide technique and LF dielectric spectroscopy to cover the frequency range 102-1014 Hz in a wide temperature interval. The dielectric response parallel and perpendicular to the polar c-axis is discussed. The ferroelectric transition at T
c
= 830 K is driven by a relaxational soft mode coupled with another central-mode type relaxation which both gradually disappear
on cooling in the ferroelectric phase. Below T
i
the parameters of the expected IR active amplitudon were estimated. The low-temperature permittivity increase on cooling
for the
field direction has been explained by an incipient proper ferroelectric-ferroelastic transition driven by an IR and Raman
active B2-symmetry soft mode.
Received 24 August 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: buixader@fzu.cz 相似文献
7.
H. Fehske A.P. Kampf M. Sekania G. Wellein 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):11-16
In order to clarify the physics of the crossover from a Peierls band insulator to a correlated Mott-Hubbard insulator, we
analyze ground-state and spectral properties of the one-dimensional half-filled Holstein-Hubbard model using quasi-exact numerical
techniques. In the adiabatic limit the transition is connected to the band to Mott insulator transition of the ionic Hubbard
model. Depending on the strengths of the electron-phonon coupling and the Hubbard interaction the transition is either first
order or evolves continuously across a narrow intermediate phase with finite spin, charge, and optical excitation gaps.
Received 7 July 2002 / Received in final form 21 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: holger.fehske@physik.uni-greifswald.de 相似文献
8.
Ya.G. Groda P. Argyrakis G.S. Bokun V.S. Vikhrenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):527-535
The selfconsistent diagram approximation (SCDA) is generalized for three-dimensional lattice gases with nearest neighbor repulsive
interactions. The free energy is represented in a closed form through elementary functions. Thermodynamical (phase diagrams,
chemical potential and mean square fluctuations), structural (order parameter, distribution functions) as well as diffusional
characteristics are investigated. The calculation results are compared with the Monte Carlo simulation data to demonstrate
high precision of the SCDA in reproducing the equilibrium lattice gas characteristics. It is shown that similarly to two-dimensional
systems the specific statistical memory effects strongly influence the lattice gas diffusion in the ordered states.
Received 7 August 2002 / Received in final form 22 January 2003 Published online 24 April 2003 相似文献
9.
M.E.S. Borelli H. Kleinert A.M.J. Schakel 《The European physical journal. E, Soft matter》2001,4(2):217-221
A stack of tensionless membranes with nonlinear curvature energy and vertical harmonic interaction is studied. At low temperatures,
the system forms a lamellar phase. At a critical temperature, the stack disorders vertically in a melting-like transition.
Received 26 April 2000 and Received in final form 16 August 2000 相似文献
10.
R. Citro M. Marinaro 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):55-60
Within a strong-coupling perturbative approach, based on a Cumulant Expansion of the extended single-band Hubbard model, we
show that the on-shell inverse scattering time deviates from the normal Fermi-liquid behavior near the points of the Fermi
surface connected by the characteristic wave-vector of an incommensurate charge density wave. The violation of the Fermi liquid
behavior is associated with a square root behavior of the inverse quasiparticle lifetime in proximity of a stripe phase. Some
relevant features observed in ARPES experiments on Bi2212 are qualitatively reproduced.
Received 28 February 2002 / Received in final form 7 May 2002 Published online 9 July 2002 相似文献
11.
D. Starešinić A. Kiš K. Biljaković B. Emerling J. W. Brill J. Souletie H. Berger F. Lévy 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):71-77
Specific heats of the charge-density-wave compounds o-TaS3 and (TaSe4)2I have been measured over the wide temperature interval 10 K-300 K. Both systems exhibit strong non-Debye behavior. Very weak
and broad anomalies are observed at the Peierls transition temperatures. For o-TaS3, the change in the curvature of the specific heat occurs at temperature of 40 K where glass transition has been deduced from
dielectric measurements, and an extended scaling analysis suggests that the glass transition is associated with a dynamical
cross over in length scales. We briefly discuss the characteristics and physical origins of the anomalies at both the Peierls
and glass transitions.
Received 5 April 2002 / Received in final form 28 June 2002 Published online 17 September 2002 相似文献
12.
We study the force-induced unfolding of random disordered RNA or single-stranded DNA polymers. The system undergoes a second-order
phase transition from a collapsed globular phase at low forces to an extensive necklace phase with a macroscopic end-to-end
distance at high forces. At low temperatures, the sequence inhomogeneities modify the critical behaviour. We provide numerical
evidence for the universality of the critical exponents which, by extrapolation of the scaling laws to zero force, contain
useful information on the ground-state (f = 0) properties. This provides a good method for quantitative studies of scaling exponents characterizing the collapsed globule.
In order to get rid of the blurring effect of thermal fluctuations, we restrict ourselves to the ground state at fixed external
force. We analyze the statistics of rearrangements, in particular below the critical force, and point out its implications
for force-extension experiments on single molecules.
Received 18 June 2002 and Received in final form 23 September 2002
RID="a"
ID="a"e-mail: muller@ipno.in2p3.fr 相似文献
13.
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
14.
C. Lorthioir P. Auroy B. Deloche Y. Gallot 《The European physical journal. E, Soft matter》2002,7(3):261-266
The chain segment dynamics in the bulk lamellar phase of polystyrene-polydimethylsiloxane (PS-PDMS) block copolymers has been
probed by NMR. The experiments were performed on a PS-PDMS diblock and on a PS-PDMS-PS triblock with twice the molecular weight.
In the diblock, at room temperature, the PDMS block segments undergo uniaxial reorientations around the normal to the lamellae.
In the triblock, the reorientational motions exhibit a lower degree of symmetry: deviations from a uniaxial dynamics are observed.
Such a behaviour originates in the anchorage of both PDMS chain ends into the PS glassy layers.
Received 27 September 2001 and Received in final form 18 January 2002 相似文献
15.
Z. Kvitek J. Bornarel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):153-160
The phase front during the 218 K transition in KD2PO4 crystals under a thermal gradient perpendicular to the c ferroelectric axis is observed to have a factory-roof shape. This shape is studied versus the magnitude of Ge in samples cut with faces in (100), (010), (001) planes or in (
0), (110), (001) ones. A geometric approach as well as the calculation of the elastic-strain energy caused by lattice misfits
along the phase front demonstrate the incoherent interface nature of the phase front. Furthemore, the results and their interpretation
allow to predict the sign of the lattice deformation u
xx
( > 0).
Received 25 April 2002 Published online 29 November 2002 相似文献
16.
A nanosecond scale in situ probe reveals that a bulk linear polymer undergoes a sharp phase transition as a function of the degree of conversion, as
it nears the glass transition. The scaling behaviour is in the same universality class as percolation. The exponents γ and
β are found to be 1.7±0.1 and 0.41±0.01 in agreement with the best percolation results in three dimensions.
Received 29 August 2002
RID="a"
ID="a"e-mail: erzan@gursey.gov.tr e-mail: erzan@itu.edu.tr 相似文献
17.
T. Breczewski I. Peral G. Madariaga 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(2):171-176
The ferroelastic domain structure and the phase boundaries of TMCC have been studied in the temperature range 114-90 K by
direct observation under polarised light. By applying an external, compressive and unidirectional mechanical stress the ferroelastic
character of the domain structure has been confirmed. The orientation of the domain walls and phase boundaries are analysed.
To characterise quantitatively the observed domain wall distribution the classical symmetry approach, based on the criterion
of spontaneous strain compatibility, has to be extended to allow small rotations of the domain walls with respect to their
ideal orientation. The observed switching process among the different domains can be understood as a mechanism that minimises
the elastic energy.
Received 21 July 2000 相似文献
18.
U. Yurtsever D. Strekalov J.P. Dowling 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):365-371
A quantum gravity-gradiometer consists of two spatially separated ensembles of atoms interrogated by pulses of a common laser
beam. The laser pulses cause the probability amplitudes of atomic ground-state hyperfine levels to interfere, producing two,
motion-sensitive, phase shifts, which allow the measurement of the average acceleration of each ensemble, and, via simple
differencing, of the acceleration gradient. Here we propose entangling the quantum states of atoms from the two ensembles
prior to the pulse sequence, and show that entanglement encodes their relative acceleration in a single interference phase
which can be measured directly, with no need for differencing.
Received 6 June 2002 / Received in final form 25 October 2002 Published online 28 January 2003 相似文献
19.
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
20.
S. Fratini P. Quémerais 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):41-49
We consider a three dimensional Wigner crystal of electrons lying in a host ionic dielectric. Owing to their interaction with
the lattice polarization, each localized electron forms a polaron. We study the collective excitations of such a polaronic
Wigner crystal at zero temperature, taking into account the quantum fluctuations of the polarization within the Feynman harmonic
approximation. We show that, contrary to the ordinary electron crystal, the system undergoes a polarization catastrophe when
the density is increased. An optical signature of this instability is derived, whose trend agrees with the experiments carried
out in Nd-based cuprates.
Received 4 July 2002 Published online 17 September 2002 相似文献