31,870 research outputs found
Intrinsic double-peak structure of the specific heat in low-dimensional quantum ferrimagnets
Motivated by recent magnetic measurements on A3Cu3(PO4)4 (A=Ca,Sr) and
Cu(3-Clpy)2(N3)2 (3-Clpy=3-Chloropyridine), both of which behave like
one-dimensional ferrimagnets, we extensively investigate the ferrimagnetic
specific heat with particular emphasis on its double-peak structure. Developing
a modified spin-wave theory, we reveal that ferromagnetic and antiferromagnetic
dual features of ferrimagnets may potentially induce an extra low-temperature
peak as well as a Schottky-type peak at mid temperatures in the specific heat.Comment: 5 pages, 6 figures embedded, Phys. Rev. B 65, 214418 (2002
Modulation of a Chirp Gravitational Wave from a Compact Binary due to Gravitational Lensing
A possible wave effect in the gravitational lensing phenomenon is discussed.
We consider the interference of two coherent gravitational waves of slightly
different frequencies from a compact binary, due to the gravitational lensing
by a galaxy halo. This system shows the modulation of the wave amplitude. The
lensing probability of such the phenomenon is of order 10^{-5} for a high-z
source, but it may be advantageous to the observation due to the magnification
of the amplitude.Comment: 3 pages, PRD in pres
Ground State Property of an Alternating Spin Ladder Involving Two Kinds of Inter-Chain Interactions
The ground state property of the alternating spin ladder is studied in the
case that the system involves an antiferromagnetic intra-chain interaction as
well as two kinds of inter-chain interactions; one is between spins of the same
magnitude and the other is between spins with different magnitudes. The
calculation has been carried out by the exact diagonalization method. As a
consequence of the competition among interactions, the system is revealed to
show an interesting variety of phases in the ground state property. Its phase
diagram is exhibited in the parameter space of the system. We find that,
however small the total amount of the inter-chain interactions is, the
ferrimagnetic ground state becomes unstable in a certain region. In this case,
which of the ferrimagnetic and the singlet ground state to appear is determined
only by the ratio between the inter-chain interactions regardless of their
total amount. The nature of two phases appearing in the singlet region of the
phase diagram and the type of the phase transition between them are also
discussed. The results are ensured by comparing with those of obtained in other
models which are contained in our model as special limiting cases.Comment: 12 pages, 9 PostScript figure
Extended-soft-core Baryon-Baryon Model II. Hyperon-Nucleon Interaction
The YN results are presented from the Extended-soft-core (ESC) interactions.
They consist of local- and non-local-potentials due to (i) One-boson-exchange
(OBE), with pseudoscalar-, vector-, scalar-, and axial-vector-nonets, (ii)
Diffractive exchanges, (iii) Two-pseudoscalar exchange, and (iv)
Meson-pair-exchange (MPE). This model, called ESC04, describes NN and YN in a
unified way using broken flavor SU(3)-symmetry. Novel ingredients are the
inclusion of (i) the axial-vector-mesons, (ii) a zero in the scalar- and
axial-vector meson form factors. We describe simultaneous fits to the NN- and
YN-data, using four options in the ESC-model. Very good fits were obtained.
G-matrix calculations with these four options are also reported. The obtained
well depths (U_\Lambda, U_\Sigma, U_\Xi) reveal distinct features of ESC04a-d.
The \Lambda\Lambda-interactions are demonstrated to be consistent with the
observed data of_{\Lambda\Lambda}^6He. The possible three-body effects are
investigated by considering phenomenologically the changes of the vector-meson
masses in a nuclear medium.Comment: preprint vesion 66 pages, two-column version 27 pages, 17 figure
Fermi surface and antiferromagnetism in the Kondo lattice: an asymptotically exact solution in d>1 Dimensions
Interest in the heavy fermion metals has motivated us to examine the quantum
phases and their Fermi surfaces within the Kondo lattice model. We demonstrate
that the model is soluble asymptotically exactly in any dimension d>1, when the
Kondo coupling is small compared with the RKKY interaction and in the presence
of antiferromagnetic ordering. We show that the Kondo coupling is exactly
marginal in the renormalization group sense, establishing the stability of an
ordered phase with a small Fermi surface, AFs. Our results have implications
for the global phase diagram of the heavy fermion metals, suggesting a Lifshitz
transition inside the antiferromagnetic region and providing a new perspective
for a Kondo-destroying antiferromagnetic quantum critical point.Comment: 4 pages, 4 figures; (v2) corrected typos and added
reference/acknowledgment; (v3) version as published in Physical Review
Letters (July, 2007
Faithful qubit distribution assisted by one additional qubit against collective noise
We propose a distribution scheme of polarization states of a single photon
over collective-noise channel. By adding one extra photon with a fixed
polarization, we can protect the state against collective noise via a
parity-check measurement and post-selection. While the scheme succeeds only
probabilistically, it is simpler and more flexible than the schemes utilizing
decoherence-free subspace. An application to BB84 protocol through collective
noise channel, which is robust to the Trojan horse attack, is also given.Comment: 4 pages, 3 figures; published version in Phys. Rev. Let
A molecular dynamics simulation of polymer crystallization from oriented amorphous state
Molecular process of crystallization from an oriented amorphous state was
reproduced by molecular dynamics simulation for a realistic polyethylene model.
Initial oriented amorphous state was obtained by uniaxial drawing an isotropic
glassy state at 100 K. By the temperature jump from 100 K to 330 K, there
occurred the crystallization into the fiber structure, during the process of
which we observed the developments of various order parameters. The real space
image and its Fourier transform revealed that a hexagonally ordered domain was
initially formed, and then highly ordered crystalline state with stacked
lamellae developed after further adjustment of the relative heights of the
chains along their axes.Comment: 4 pages, 3 figure
Modified spin-wave theory of nuclear magnetic relaxation in one-dimensional quantum ferrimagnets: Three-magnon versus Raman processes
Nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is
studied by means of a modified spin-wave theory. Calculating beyond the
first-order mechanism, where a nuclear spin directly interacts with spin waves
through the hyperfine coupling, we demonstrate that the
exchange-scattering-enhanced three-magnon nuclear relaxation may generally
predominate over the Raman one with increasing temperature and decreasing
field. Recent proton spin-lattice relaxation-time (T_1_) measurements on the
ferrimagnetic chain compound NiCu(C_7_H_6_N_2_O_6_)(H_2_O)_3_2H_2_O suggest
that the major contribution to 1/T_1_ be made by the three-magnon scattering.Comment: 8 pages, 5 figure
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On the Elevated Temperature Thermal Stability of Nanoscale Mn-Ni-Si Precipitates Formed at Lower Temperature in Highly Irradiated Reactor Pressure Vessel Steels.
Atom probe tomography (APT) and scanning transmission electron microscopy (STEM) techniques were used to probe the long-time thermal stability of nm-scale Mn-Ni-Si precipitates (MNSPs) formed in intermediate and high Ni reactor pressure vessel steels under high fluence neutron irradiation at ≈320 °C. Post irradiation annealing (PIA) at 425 °C for up to 57 weeks was used to determine if the MNSPs are: (a) non-equilibrium solute clusters formed and sustained by radiation induced segregation (RIS); or, (b) equilibrium G or Γ2 phases, that precipitate at accelerated rates due to radiation enhanced diffusion (RED). Note the latter is consistent with both thermodynamic models and x-ray diffraction (XRD) measurements. Both the experimental and an independently calibrated cluster dynamics (CD) model results show that the stability of the MNSPs is very sensitive to the alloy Ni and, to a lesser extent, Mn content. Thus, a small fraction of the largest MNSPs in the high Ni steel persist, and begin to coarsen at long times. These results suggest that the MNSPs remain a stable phase, even at 105 °C higher than they formed at, thus are most certainly equilibrium phases at much lower service relevant temperatures of ≈290 °C
Simulated nuclear spin-lattice relaxation in Heisenberg ferrimagnets: Indirect observation of quadratic dispersion relations
In response to recent proton spin relaxation-time measurements on
NiCu(pba)(HO)2HO with ,
which is an excellent one-dimensional ferrimagnetic Heisenberg model system of
spin-, we study the Raman relaxation process in spin- quantum
ferrimagnets on the assumption of predominantly dipolar hyperfine interactions
between protons and magnetic ions. The relaxation time is formulated
within the spin-wave theory and is estimated as a function of temperature and
an applied field by a quantum Monte Carlo method. The low-temperature
behavior of the relaxation rate qualitatively varies with ,
while is almost proportional to due to the characteristic
dispersion relations.Comment: 5 pages, 3 figures embedded, to appear in Phys. Rev. B Rapid Commu
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