1,156 research outputs found
N\'eel and singlet RVB orders in the t-J model
The N\'eel and the singlet RVB orders of the {\it t-J} model in a 2D square
lattice are studied in the slave-boson mean-field approximation. It is shown
that the N\'eel order parameter takes the maximum value at the finite
temperature and disappear at the lower temperature for a certain range of
doping. It is also shown that the N\'eel and the singlet RVB orders coexist at
low temperature. This suggests the possibility of the coexistence of the N\'eel
and the superconducting orders.Comment: RevTeX, 8 pages, 1 postscript figure. To appear in Physica C, Volume
257, issue 38
Static and dynamic properties of frictional phenomena in a one-dimensional system with randomness
Static and dynamic frictional phenomena at the interface with random
impurities are investigated in a two-chain model with incommensurate structure.
Static frictional force is caused by the impurity pinning and/or by the pinning
due to the regular potential, which is responsible for the breaking of
analyticity transition for impurity-free cases. It is confirmed that the static
frictional force is always finite in the presence of impurities, in contrast to
the impurity-free system. The nature of impurity pinning is discussed in
connection with that in density waves. The kinetic frictional force of a steady
sliding state is also investigated numerically. The relationship between the
sliding velocity dependence of the kinetic frictional force and the strength of
impurity potential is discussed.Comment: RevTex, 14 pages, 6 PostScript figures, to appear in Phys. Rev.
Dynamical frictional phenomena in an incommensurate two-chain model
Dynamical frictional phenomena are studied theoretically in a two-chain model
with incommensurate structure. A perturbation theory with respect to the
interchain interaction reveals the contributions from phonons excited in each
chain to the kinetic frictional force. The validity of the theory is verified
in the case of weak interaction by comparing with numerical simulation. The
velocity and the interchain interaction dependences of the lattice structure
are also investigated. It is shown that peculiar breaking of analyticity states
appear, which is characteristic to the two-chain model. The range of the
parameters in which the two-chain model is reduced to the Frenkel-Kontorova
model is also discussed.Comment: RevTex, 9 pages, 7 PostScript figures, to appear in Phys. Rev.
Friction, order, and transverse pinning of a two-dimensional elastic lattice under periodic and impurity potentials
Frictional phenomena of two-dimensional elastic lattices are studied
numerically based on a two-dimensional Frenkel-Kontorova model with impurities.
It is shown that impurities can assist the depinning. We also investigate
anisotropic ordering and transverse pinning effects of sliding lattices, which
are characteristic of the moving Bragg glass state and/or transverse glass
state. Peculiar velocity dependence of the transverse pinning is observed in
the presence of both periodic and random potentials and discussed in the
relation with growing order and discommensurate structures.Comment: RevTeX, 4 pages, 5 figures. to appear in Phys. Rev. B Rapid Commu
Effect of Local Inhomogeneity on Nucleation; Case of Charge Density Wave Depinning
The spatial inhomogeneities are expected to affect nucleation process in an
essential way. These effects are studied theoretically by considering the case
of the depinning of the charge density wave as a typical example. The threshold
field of the depinning of the one-dimensional commensurate charge density wave
with one impurity has been examined classically based on the phase Hamiltonian
at absolute zero. It is found that the threshold field is lowered by a finite
amount compared to that in the absence of an impurity.Comment: pages 12, LaTeX, 9 figures, uses jpsj.sty, submitted to J. Phys. Soc.
Jp
Theoretical Study of Friction: A Case of One-Dimensional Clean Surfaces
A new method has been proposed to evaluate the frictional force in the
stationary state. This method is applied to the 1-dimensional model of clean
surfaces. The kinetic frictional force is seen to depend on velocity in
general, but the dependence becomes weaker as the maximum static frictional
force increases and in the limiting case the kinetic friction gets only weakly
dependent on velocity as described by one of the laws of friction. It is also
shown that there is a phase transition between state with vanishing maximum
static frictional force and that with finite one. The role of randomness at the
interface and the relation to the impurity pinning of the sliding
Charge-Density-Wave are discussed. to appear in Phys.Rev.B. abstract only. Full
text is available upon request. E-mail: [email protected]: 2 pages, Plain TEX, OUCMT-94-
Crossover from 2-dimensional to 1-dimensional collective pinning in NbSe3
We have fabricated NbSe structures with widths comparable to the
Fukuyama-Lee-Rice phase-coherence length. For samples already in the
2-dimensional pinning limit, we observe a crossover from 2-dimensional to
1-dimensional collective pinning when the crystal width is less than 1.6
m, corresponding to the phase-coherence length in this direction. Our
results show that surface pinning is negligible in our samples, and provide a
means to probe the dynamics of single domains giving access to a new regime in
charge-density wave physics.Comment: 4 pages, 2 figures, and 1 table. Accepted for publication in Physical
Review
Resistive relaxation in field-induced insulator-metal transition of a (LaPr)SrMnO bilayer manganite single crystal
We have investigated the resistive relaxation of a
(LaPr)SrMnO single crystal, in
order to examine the slow dynamics of the field-induced insulator to metal
transition of bilayered manganites. The temporal profiles observed in remanent
resistance follow a stretched exponential function accompanied by a slow
relaxation similar to that obtained in magnetization and magnetostriction data.
We demonstrate that the remanent relaxation in magnetotransport has a close
relationship with magnetic relaxation that can be understood in the framework
of an effective medium approximation by assuming that the first order parameter
is proportional to the second order one.Comment: 6 pages,5 figure
Social structure and reproduction of long-tailed porcupine (Trichys fasciculata)
We studied the social structure of long-tailed porcupine (Trichys fasciculata) in the tropical rainforest in Sabah, Borneo Island, Malaysia via direct observation assisted by radio-tracking and camera-trapping at burrow entrances. We identified and observed seven individuals in the study area, of which five were radio-tagged. Analysis of their burrow use, home range, and behaviour strongly suggested that five of the observed individuals formed a family group consisting of an adult male–female pair and their three offspring, two of which were born during the study period. The family members used the same burrow site almost every day, and their home ranges largely overlapped. In contrast, the other two individuals never used the burrow sites of this family group. The adult male–female pair was maintained for at least 18 months and reproduced twice during the study period. They had a litter size of one, and the inter-litter interval was estimated to be 11 months. During these two reproductions, the previous litter stayed in the natal family group as a sub-adult after the next juvenile was born. Direct paternal care, such as grooming the juvenile, was also observed. Their low reproductive potential should be considered in conservation efforts
- …