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1.
G. Vilasi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(2):207-210
Melnikov-method-based theoretical results are demonstrated concerning the relative effectiveness of any two weak excitations in suppressing homoclinic/heteroclinic chaos of a relevant class of dissipative, low-dimensional and
non-autonomous systems for the main resonance between the chaos-inducing and chaos-suppressing excitations. General analytical
expressions are derived from the analysis of generic Melnikov functions providing the boundaries of the regions as well as
the enclosed area in the amplitude/initial phase plane of the chaos-suppressing excitation where homoclinic/heteroclinic chaos
is inhibited. The relevance of the theoretical results on chaotic attractor elimination is confirmed by means of Lyapunov
exponent calculations for a two-well Duffing oscillator.
Received 21 May 2002 / Received in final form 13 September 2002 Published online 29 November 2002 相似文献
2.
T. Ruf 《Applied Physics A: Materials Science & Processing》2003,76(1):21-26
Inelastic X-ray scattering with meV resolution has recently become available for studies of dynamical properties and elementary
excitations in solids. Contrary to Raman spectroscopy at visible wavelengths, which in first order is limited to the Brillouin-zone
center, the wave vectors in hard X-ray Raman scattering are very large, and the crystal-momentum transfer to elementary excitations,
whose energies may range from a few meV up to several eV, can be tuned continuously across the whole Brillouin zone. This
paper reviews new and unique possibilities offered by X-ray Raman spectroscopy for crystalline solids, such as phonon-dispersion
measurements (GaN), the determination of phonon self-energies (isotopically mixed diamond), and resonance effects and studies
of electronic excitations (copper oxides).
Received: 19 October 2001 / Accepted: 12 December 2001 / Published online: 27 March 2002 / Published online: 27 March 2002
RID="*"
ID="*"Present address: Agilent Technologies Deutschland GmbH, Herrenberger Str. 130, 71034 B?blingen, Germany 相似文献
3.
D.M. Newman M.L. Wears R. Atkinson D. McHugh 《Applied physics. B, Lasers and optics》2002,74(7-8):715-718
The concept of using comparison between magneto-optic measurements taken in the linear and second-harmonic reflected fields
to address problems attending the development of ultra-high-density recording media as the limits of thermal stability are
approached is presented. It is shown how magneto-optical measurements made routinely in the linear reflected field to access
many of the bulk characteristics of such media may, by operating in the second-harmonic field, be fruitfully extended. To
illustrate the techniques being explored, reference is made to initial measurements on a longitudinal recording medium under
continuing development at Coventry. This medium, already shown to support recording at linear densities in excess of 100 kfci,
is based on cobalt particles around 10 nm in diameter.
Received: 16 October 2001 / Revised version: 14 March 2002 / Published online: 29 May 2002 相似文献
4.
O. Pfennigstorf A. Petkova Z. Kallassy M. Henzler 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):111-115
The dipole modes of non-parabolic quantum dots are studied by means of their current and density patterns as well as with
their local absorption distribution. The anticrossing of the so-called Bernstein modes originates from the coupling with electron-hole
excitations of the two Landau bands which are occupied at the corresponding magnetic fields. Non-quadratic terms in the potential
cause an energy separation between bulk and edge current modes in the anticrossing region. On a local scale the fragmented
peaks absorb energy in complementary spatial regions which evolve with the magnetic field.
Received 3 December 2001 / Received in final form 5 April 2002 Published online 9 July 2002 相似文献
5.
V.D. Natsik Y.I. Nazarenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):285-289
The problem of crowdion motion is formulated and analyzed as a dynamical problem of a three-dimensional crystal lattice formed
by atoms of several kinds, which interact with each other by means of short-range pair potentials. It is explained that in
order for the the crowdion excitations of the close-packed atomic rows to be distinguishable against the background of small
dynamic deformations of the crystal as a whole, the microscopic parameters of the crystal structure must meet certain stated
requirements. The equation of motion of a crowdion in an arbitrary elastic strain field of the crystal is derived in the Lagrangian
formalism. Expressions are obtained which relate the effective mass and the rest energy of a crowdion with the geometric and
force parameters of the crystal lattice.
Received 4 October 2001 / Received in final form 27 February 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: nazarenko@ksame.kharkov.ua 相似文献
6.
M.T. Primatarowa K.T. Stoychev R.S. Kamburova 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):291-294
We investigate the propagation and interaction of solitons associated with circularly polarized vibrations in gyrotropic media.
The chirality of the structure yields different dispersion laws and hence different phase and group velocities for the left-
and right-handed modes. The helical arrangement of the monomers is modelled through first- and third-neighbour interactions.
The dynamics of the excitations is governed by a system of coupled discrete nonlinear Schr?dinger equations which is studied
both analytically and numerically. Depending on the initial conditions and the interaction constants, different evolutionary
patterns are obtained corresponding to unbound or bound one- and two-soliton solutions. The results can be applied to the
process of energy transfer in helical polymers.
Received 1st October 2001 / Received in final form 30 April 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: krad@issp.bas.bg 相似文献
7.
K. Batra V. Prasad M. Mohan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):191-198
The scattering of heavy ion with a multilevel Rydberg atom in the presence of an electromagnetic field is studied. The interaction
of Rydberg atom and the e.m field is explored using non-perturbative quasi-energy technique. Although the results are presented
for selected excitations but in actual calculations we have included many levels of the atom. The effect of various parameters
are shown on collisional excitation process. As an illustration detailed calculations are performed for the inelastic proton-Na
Rydberg atom collision accompanied by the transfer of photons and the effects of dressing due to the field are considered.
The emphasis of the present work is on collision induced transitions especially the case that involves change of orbital as
well as principal quantum number.
Received 26 December 2001 / Received in final form 8 April 2002 Published online 19 July 2002 相似文献
8.
M. Amoruso I. Meccoli A. Minguzzi M.P. Tosi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(3):441-447
We evaluate the small-amplitude excitations of a spin-polarized vapour of Fermi atoms confined inside a harmonic trap. The
dispersion law is obtained for the vapour in the collisional regime inside a spherical trap of frequency , with n the number of radial nodes and the orbital angular momentum. The low-energy excitations are also treated in the case of an axially symmetric harmonic confinement.
The collisionless regime is discussed with main reference to a Landau-Boltzmann equation for the Wigner distribution function:
this equation is solved within a variational approach allowing an account of non-linearities. A comparative discussion of
the eigenmodes of oscillation for confined Fermi and Bose vapours is presented in an Appendix.
Received 23 February 1999 and Received in final form 21 April 1999 相似文献
9.
T. Buishvili N. Giorgadze R. Khomeriki L. Tkeshelashvili 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(4):515-517
Paper investigates the onset of nuclear magnetic ordering caused by the indirect Suhl-Nakamura interaction in ferromagnets.
The necessary condition for nuclear spin ordering with definite ordering vector is obtained. Particularly, it is shown that
ferromagnetically ordered phase of nuclear spins could be observed only in case of disk shaped samples. The spectrum of the
nuclear spin excitations is also found.
Received 25 January 1999 and Received in final form 5 May 1999 相似文献
10.
We study the static scalar susceptibility of the nuclear medium, i.e., the change of the quark condensate for a small modification of the quark mass. In the linear sigma model it is linked to
the in-medium sigma propagator and its magnitude increases due to the mixing with the softer modes of the nucleon-hole excitations.
We show that the pseudoscalar susceptibility, which is large in the vacuum, owing to the smallness of the pion mass, follows
the density evolution of the quark condensate and thus decreases. At normal nuclear matter density the two susceptibilities
become much closer, a partial chiral symmetry restoration effect as they become equal when the full restoration is achieved.
Received: 20 July 2002 / Accepted: 14 September 2002 / Published online: 21 January 2003
RID="a"
ID="a"e-mail: chanfray@ipnl.in2p3.fr
Communicated by A. Molinari 相似文献
11.
Feng Zhai Yong Guo Bing-Lin Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(1):147-152
We adopt the group velocity approach to the issue of tunneling time in two configurations of magnetic barrier structures,
which are arranged with identical or unidentical building blocks. The effects of an external electric field are also taken
into account. The tunneling time in magnetic barrier structures is found to be strongly dependent on the magnetic configuration,
the applied bias, the incident energy as well as the longitudinal wave vector. The results indicate that for electrons with
equal energy but different incident angles, the tunneling processes are significantly separated in time within the same magnetic
barrier structure. In the configuration arranged with unidentical building blocks, there exists obvious asymmetry of tunneling
time in two opposite tunneling directions. Such a discrepancy of the tunneling time varies distinctly with the longitudinal
wave vector and the applied bias.
Received 4 March 2002 / Received in final form 22 May 2002 Published online 17 September 2002 相似文献
12.
C. Mavroyannis 《Applied physics. B, Lasers and optics》2003,76(1):75-81
Analytical expressions of the spectral functions have been derived for a number of induced excitations that occur near the
difference-frequency generation in a four-level atomic system interacting with three laser fields. The spectral heights and
subnatural line widths of the induced peaks depend on the intensities of the laser fields involved. The maximum heights of
the induced peaks take positive, zero and negative values, indicating that the processes of absorption (attenuation), dark
resonance and stimulated emission (amplification) are likely to occur near the difference-frequency generation, respectively.
Received: 15 March 2002 / Revised version: 17 June 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +1-613-954-5242 相似文献
13.
Y. Fukumoto 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):167-171
Three-dimensional motion of a slender vortex tube, embedded in an inviscid incompressible fluid, is investigated under the
localized induction approximation for the Euler equations. Using the method of matched asymptotic expansions in a small parameter ε, the ratio of core radius
to curvature radius, the velocity of a vortex filament is derived to O(ε3), whereby the influence of elliptical deformation of the core due to the self-induced strain is taken into account. It is
found that there is an integrable line in the core whose evolution obeys a summation of the first and third terms of the localized induction hierarchy.
Received 2 October 2001 / Received in final form 10 May 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: yasuhide@math.kyushu-u.ac.jp 相似文献
14.
O.I. Yordanov I.S. Atanasov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):211-215
We consider general d-dimensional random surfaces that are characterized by power-law power spectra defined in both infinite and finite spectral
regions. The first type of surfaces belongs to the class of ideal fractals, whereas the second possess both the smallest and
the largest scales and physically is more realistic. For both types we calculate the structure functions (SF) exactly; in
addition for the second type we obtain the SF's asymptotic expansions. On this basis we show that the surfaces are (in statistical
sense) self-affine and approximately self-affine, respectively. Depending on the value of the spectral exponent, we find imbalance
between the finite size effects which results in systematic discrepancy in the scaling properties between the two types of
surfaces. Explicit expressions for the topothesy, and in the case of second type of surfaces for the large correlation length
and cross-over distances are also derived.
Received 3 October 2001 / Received in final form 5 March 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: oyordanov@aubg.bg 相似文献
15.
N. Cavadini Th. Strässle P. Allenspach P.C. Canfield Ph. Bourges 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):377-384
The magnetic excitations in the antiferromagnetic phase of HoNi2B2C are studied by inelastic neutron scattering on single crystals for the first time. Spectra measured at constant T
= 2 K along symmetry directions of the reciprocal space are well explained in terms of crystal electric field (CEF) magnetic
excitons within the J
= 8 ground state multiplet of Ho3+. Very modest bandwidth with planar energy dispersion describes the magnetic exciton dynamics. A perturbative model approach
consisting of the CEF states in the effective exchange mean-field provides a simple but applicable characterization of the
experimental observations. The microscopic determination of the relevant exchange parameters is discussed in connection with
previous works on the subject.
Received 25 February 2002 / Received in final form 13 May 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: nordal.cavadini@psi.ch 相似文献
16.
H. Meyer-Ortmanns T. Reisz 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):549-558
Dynamical linked cluster expansions are linked cluster expansions with hopping parameter terms endowed with their own dynamics.
We discuss physical applications to systems with annealed and quenched disorder. Examples are the bond-diluted Ising model
and the Sherrington-Kirkpatrick spin glass. We derive the rules and identify the full set of graphs that contribute to the
series in the quenched case. This way it becomes possible to avoid the vague extrapolation from positive integer n to n = 0, that usually goes along with an application of the replica trick.
Received 13 December 2001
Published online 25 June 2002 相似文献
17.
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
18.
Yu.A. Fridman D.V. Spirin 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):311-313
The quantum spherical XY model with orthorhombic anisotropy is investigated. It is shown that in contradiction with the results
of reference [#!9!#], the long-range magnetic order is stabilized in two dimensions. Both analytical and numerical results
are presented. The incorrect results of the work [9] are explained to be the result of improper choice of quantization axis.
Received 26 August 2002 / Received in final form 24 October 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: frid@tnu.crimea.ua 相似文献
19.
Y. Pavlyukh W. Hübner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):239-246
We present a method for the numerical investigation of the electron dynamics in small metallic clusters in intense laser fields.
We obtain information about collective excitations and relaxation processes in the Na
9
+
and Pt3 clusters analyzing the power spectrum of the dipole moment within a mean-field approach. The power spectrum is computed for
various laser pulse parameters as well as for the limit of an infinitely short laser pulse. Due to the basis set expansion
of the wave function our method is capable to follow the dynamics not only of the whole electron cloud, but of any particular
molecular orbital.
Received 28 March 2002 / Received in final form 31 May 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: pavlyukh@mpi-halle.de 相似文献
20.
M.L. Chiofalo M. Polini M.P. Tosi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):371-378
We study the dispersion relation of the excitations of a dilute Bose-Einstein condensate confined in a periodic optical potential
and its Bloch oscillations in an accelerated frame. The problem is reduced to one-dimensionality through a renormalization
of the s-wave scattering length and the solution of the Bogolubov-de Gennes equations is formulated in terms of the appropriate Wannier
functions. Some exact properties of a periodic one-dimensional condensate are easily demonstrated: (i) the lowest band at
positive energy refers to phase modulations of the condensate and has a linear dispersion relation near the Brillouin zone
centre; (ii) the higher bands arise from the superposition of localized excitations with definite phase relationships; and
(iii) the wavenumber-dependent current under a constant force in the semiclassical transport regime vanishes at the zone boundaries.
Early results by Slater [Phys. Rev. 87, 807 (1952)] on a soluble problem in electron energy bands are used to specify the conditions under which the Wannier functions
may be approximated by on-site tight-binding orbitals of harmonic-oscillator form. In this approximation the connections between
the low-lying excitations in a lattice and those in a harmonic well are easily visualized. Analytic results are obtained in
the tight-binding scheme and are illustrated with simple numerical calculations for the dispersion relation and semiclassical
transport in the lowest energy band, at values of the system parameters which are relevant to experiment.
Received 3 December 1999 and Received in final form 22 March 2000 相似文献