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21.
I. Titvinidze G.I. Japaridze 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):383-393
The quantum phase transition in the ground state of the extended spin S
= 1/2 XY model has been studied in detail. Using the exact solution of the model the low temperature thermodynamics, as well as the
ground state phase diagram of the model in the presence of applied uniform and/or staggered magnetic field are discussed.
Received 29 November 2002 / Received in final form 24 February 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: japa@iph.hepi.edu.ge 相似文献
22.
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
23.
D. Batani F. Strati B. Telaro Th. Löwer T. Hall A. Benuzzi-Mounaix M. Koenig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):99-107
In this paper we describe the quality requirements that a shock wave must fulfil to make equation of state (EOS) measurements
possible: planarity, no-preheating and stationarity of the shock. Experimental measurements have been performed at the Max
Planck Institut für Quantenoptik (Garching). We also present simple analytical models that allow to verify shock stationarity
and absence of preheating.
Received 17 June 2002 Published online 21 January 2003
RID="a"
ID="a"e-mail: batani@mib.infn.it
RID="b"
ID="b"Present address: Pro-beam, Behrinsta?e 6, 85152 Planegg b. München, Germany.
RID="c"
ID="c"UMR 7605 相似文献
24.
S. Borodziuk A. Kasperczuk T. Pisarczyk S. Yu. Gus'kov J. Ullschmied E. Krousky K. Masek M. Pfeifer K. Rohlena J. Skala M. Kalal J. Limpouch P. Pisarczyk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):311-317
Efficiency studies of laser driven thin metal disks
acceleration using the first harmonic (λ1=1.315 μm) of
the Prague Asterix Laser System (PALS) and subsequent craters creation
produced by collisions of these disks with massive targets are presented.
Several different disks made of aluminium and copper foils with diameters of
300 μm and 600 μm and thicknesses of 11 μm (Al) and 3.6 μ
m (Cu) were employed. Disks were placed at the distance of either 100 μ
m or 300 μm in front of aluminium massive targets. The following
irradiation conditions were used: the laser beam energy of 120 J, the focal
spot diameter of 200 μm, and the pulse duration of 0.4 ns (FWHM). A
three-frame interferometric system was employed to determine electron
density distributions in plasma corona. Shape and volume of craters were
obtained by crater replica technology and microscopy measurements. The aim
of these investigations was to analyse conditions leading to the most
effective energy transfer in the process of collision of the accelerated
disks with solid targets. The overall efficiency of these processes was
characterized by the volume of craters produced in such targets. 相似文献
25.
Progress in direct-drive inertial confinement fusion research at the
laboratory for laser energetics
R. L. McCrory D. D. Meyerhofer S. J. Loucks S. Skupsky R. Betti T. R. Boehly T. J.B. Collins R. S. Craxton J. A. Delettrez D. H. Edgell R. Epstein K. A. Fletcher C. Freeman J. A. Frenje V. Yu. Glebov V. N. Goncharov D. R. Harding I. V. Igumenshchev R. L. Keck J. D. Kilkenny J. P. Knauer C. K. Li J. Marciante J. A. Marozas F. J. Marshall A. V. Maximov P. W. McKenty S. F.B. Morse J. Myatt S. Padalino R. D. Petrasso P. B. Radha S. P. Regan T. C. Sangster F. H. Séguin W. Seka V. A. Smalyuk J. M. Soures C. Stoeckl B. Yaakobi J. D. Zuegel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):233-238
Direct-drive inertial confinement fusion (ICF) is
expected to demonstrate high gain on the National Ignition Facility (NIF) in
the next decade and is a leading candidate for inertial fusion energy
production. The demonstration of high areal densities in hydrodynamically
scaled cryogenic DT or D2 implosions with neutron yields that are a
significant fraction of the “clean” 1-D predictions will validate the
ignition-equivalent direct-drive target performance on the OMEGA laser at
the Laboratory for Laser Energetics (LLE). This paper highlights the
recent experimental and theoretical progress leading toward achieving this
validation in the next few years.
The NIF will initially be configured for X-ray drive and with no beams
placed at the target equator to provide a symmetric irradiation of a
direct-drive capsule. LLE is developing the “polar-direct-drive” (PDD)
approach that repoints beams toward the target equator. Initial 2-D
simulations have shown ignition. A unique “Saturn-like” plastic ring
around the equator refracts the laser light incident near the equator toward
the target, improving the drive uniformity.
LLE is currently constructing the multibeam, 2.6-kJ/beam, petawatt laser
system OMEGA EP. Integrated fast-ignition experiments, combining the OMEGA
EP and OMEGA Laser Systems, will begin in FY08. 相似文献
26.
The boundary quantum entanglement for the s = 1/2 X X Z spin chain with boundary impurities is studied via the density matrix renormalization group (DMRG) method. It is shown that the entanglement entropy of the boundary bond (the impurity and the chain spin next to it) behaves differently in different phases. The relationship between the singular points of the boundary entropy and boundary quantum critical points is discussed. 相似文献
27.
S. Chen L. Wang Y. P. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):265-270
We study the ground-state properties of frustrated Heisenberg ferrimagnetic
ladders with antiferromagnetic exchange interactions and two types of
alternating sublattice spins. In the limit of strong rung couplings, we show
that the mixed spin-1/2 and spin-1 ladders can be systematically mapped onto
a spin-1/2 Heisenberg model with additional next-nearest-neighbor exchanges.
The system is either in a ferrimagnetic state or in a critical spin-liquid
state depending on the competition between the spin exchanges along the legs
and the diagonal exchanges. 相似文献
28.
Titanium was laser nitrided by means of free-electron laser irradiation in pure nitrogen atmosphere. The variation of pulse frequency and macropulse duration of the free electron laser resulted in δ-TiNx coatings with different thickness and different micro- and macroscopic morphologies. The coatings revealed, characteristic values for hardness, roughness and crystallographic texture, which originate from the growth mechanism, the solid-liquid interface energy and the strain. Further investigations showed that the dendritic growth is beginning at the surface and that the alignment of dendrites is normal to the surface. A correlation of the texture with the time structure of the laser pulses was found. Numerical simulations were performed and compared with the experimental results. The simulations can explain the experimental results. 相似文献
29.
Pairwise thermal entanglement of an XXZ ferromagnetic chain with a uniform magnetic field is investigated by using the entanglement measure of negativity. The effects of spin, number of sites, anisotropic parameter, and magnetic field on the threshold temperature are discussed respectively. 相似文献
30.
We study the thermal entanglement properties of a simple system that includes three spins inhomogeneously coupled between them with additional anisotropy in their couplings. The main result is the systematic analysis of the concurrence evolution as functions of inhomogeneity, anisotropy and temperature. By adjusting proportional factor of the interaction J and anisotropy parameter △, the comparison between concurrences C12 andC13 is also presented. 相似文献