7,041 research outputs found
Coordinate space proton-deuteron scattering calculations including Coulomb force effects
We present a practical method to solve the proton-deuteron scattering problem
at energies above the three-body breakup threshold, in which we treat
three-body integral equations in coordinate space accommodating long-range
proton-proton Coulomb interactions. The method is examined for phase shift
parameters, and then applied to calculations of differential cross sections in
elastic and breakup reactions, analyzing powers, etc. with a realistic
nucleon-nucleon force and three-nucleon forces. Effects of the Coulomb force
and the three-nucleon forces on these observables are discussed in comparing
with experimental data.Comment: 15 pages, 14 figures, submitted to PR
Finite-temperature phase transitions in bilayer quantum Hall systems
In this paper, the influence of an in-plane magnetic field B_\parallel on the
finite-temperature phase transitions in nu=2 bilayer quantum Hall systems are
examined. It is found that there can exist two types of finite-temperature
phase transitions. The first is the Kosterlitz-Thouless (KT) transitions, which
can have an unusual non-monotonic dependence on B_\parallel; the second type
originates from the crossing of energy levels and always increases with
B_\parallel. Based on these results, we point out that the threshold
temperature observed in the inelastic light scattering experiments cannot be
the KT transition temperature, because the latter shows a totally different
B_\parallel-dependence as compared with the experimental observation. Instead,
it should be the level-crossing temperature, which we found agrees with the
B_\parallel-dependence observed. Moreover, combining the knowledge of these two
transition temperatures, a complete finite-temperature phase diagram is
presented.Comment: RevTeX, 5 pages with 3 EPS figures include
Effect of in-plane magnetic field on magnetic phase transitions in nu=2 bilayer quantum Hall systems
By using the effective bosonic spin theory, which is recently proposed by
Demler and Das Sarma [ Phys. Rev. Lett. 82, 3895 (1999) ], we analyze the
effect of an external in-plane magnetic field on the magnetic phase transitions
of the bilayer quantum Hall system at filling factor nu=2. It is found that the
quantum phase diagram is modified by the in-plane magnetic field. Therefore,
quantum phase transitions can be induced simply by tilting the magnetic field.
The general behavior of the critical tilted angle for different layer
separations and interlayer tunneling amplitudes is shown. We find that the
critical tilted angles being calculated agree very well with the reported
values. Moreover, a universal critical exponent for the transition from the
canted antiferromagnetic phase to the ferromagnetic phase is found to be equal
to 1/2 within the present effective theory.Comment: RevTeX, 4 pages with 3 EPS figures include
Singular Laplacian Growth
The general equations of motion for two dimensional Laplacian growth are
derived using the conformal mapping method. In the singular case, all
singularities of the conformal map are on the unit circle, and the map is a
degenerate Schwarz-Christoffel map. The equations of motion describe the
motions of these singularities. Despite the typical fractal-like outcomes of
Laplacian growth processes, the equations of motion are shown to be not
particularly sensitive to initial conditions. It is argued that the sensitivity
of this system derives from a novel cause, the non-uniqueness of solutions to
the differential system. By a mechanism of singularity creation, every solution
can become more complex, even in the absence of noise, without violating the
growth law. These processes are permitted, but are not required, meaning the
equation of motion does not determine the motion, even in the small.Comment: 8 pages, Latex, 4 figures, Submitted to Phys. Rev.
Doubly Enhanced Skyrmions in Bilayer Quantum Hall States
By tilting the samples in the magnetic field, we measured and compared the
Skyrmion excitations in the bilayer quantum Hall (QH) state at the Landau-level
filling factor and in the monolayer QH state at . The observed
number of flipped spins is in the bilayer system with a large
tunneling gap, and in the bilayer system with a small tunneling gap,
while it is in the monolayer system. The difference is interpreted due
to the interlayer exchange interaction. Moreover, we have observed seemingly
preferred numbers for the flipped spins by tilting bilayer
samples.Comment: 4 pages, 4 figure
Coexistence of Bloch electrons and glassy electrons in Ca10(Ir4As8)(Fe2_xIrxAs2)5 revealed by angle-resolved photoemission spectroscopy
Angle-resolved photoemission spectroscopy of Ca10(Ir4As8)(Fe2_xIrxAs2)5 shows
that the Fe 3d electrons in the FeAs layer form the hole-like Fermi pocket at
the zone center and the electron-like Fermi pockets at the zone corners as
commonly seen in various Fe-based superconductors. The FeAs layer is heavily
electron doped and has relatively good two dimensionality. On the other hand,
the Ir 5d electrons are metallic and glassy probably due to atomic disorder
related to the Ir 5d orbital instability. Ca10(Ir4As8)(Fe2_xIrxAs2)5 exhibits a
unique electronic state where the Bloch electrons in the FeAs layer coexist
with the glassy electrons in the Ir4As8 layer.Comment: 4 pages, 3 figure
Collective modes of CP(3) Skyrmion crystals in quantum Hall ferromagnets
The two-dimensional electron gas in a bilayer quantum Hall system can sustain
an interlayer coherence at filling factor nu=1 even in the absence of tunneling
between the layers. This system has low-energy charged excitations which may
carry textures in real spin or pseudospin. Away from filling factor nu =1 a
finite density of these is present in the ground state of the 2DEG and forms a
crystal. Depending on the relative size of the various energy scales, such as
tunneling (Delta_SAS), Zeeman coupling (Delta_Z) or electrical bias (Delta_b),
these textured crystal states can involve spin, pseudospin, or both
intertwined. In this article, we present a comprehensive numerical study of the
collective excitations of these textured crystals using the GRPA. For the pure
spin case, at finite Zeeman coupling the state is a Skyrmion crystal with a
gapless phonon mode, and a separate Goldstone mode that arises from a broken
U(1) symmetry. At zero Zeeman coupling, we demonstrate that the constituent
Skyrmions break up, and the resulting state is a meron crystal with 4 gapless
modes. In contrast, a pure pseudospin Skyrme crystal at finite tunneling has
only the phonon mode. For Delta_SAS=0, the state evolves into a meron crystal
and supports an extra gapless U(1) mode in addition to the phonon. For a CP(3)
Skyrmion crystal, we find a U(1) gapless mode in the presence of the
symmetry-breaking fields. In addition, a second mode with a very small gap is
present in the spectrum.Comment: 16 pages and 12 eps figure
Spontaneous alloying in binary metal microclusters - A molecular dynamics study -
Microcanonical molecular dynamics study of the spontaneous alloying(SA),
which is a manifestation of fast atomic diffusion in a nano-sized metal
cluster, is done in terms of a simple two dimensional binary Morse model.
Important features observed by Yasuda and Mori are well reproduced in our
simulation. The temperature dependence and size dependence of the SA phenomena
are extensively explored by examining long time dynamics. The dominant role of
negative heat of solution in completing the SA is also discussed. We point out
that a presence of melting surface induces the diffusion of core atoms even if
they are solid-like. In other words, the {\it surface melting} at substantially
low temperature plays a key role in attaining the SA.Comment: 15 pages, 12 fgures, Submitted to Phys.Rev.
PseudoSkyrmion Effects on Tunneling Conductivity in Coherent Bilayer Quantum Hall States at
We present a mechamism why interlayer tunneling conductivity in coherent
bilayer quantum Hall states at is anomalously large, but finite in the
recent experiment. According to the mechanism, pseudoSkyrmions causes the
finite conductivity, although there exists an expectation that dissipationless
tunneling current arises in the state. PseudoSkyrmions have an intrinsic
polarization field perpendicular to the layers, which causes the dissipation.
Using the mechanism we show that the large peak in the conductivity remains for
weak parallel magnetic field, but decay rapidly after its strength is beyond a
critical one, Tesla.Comment: 6 pages, no figure
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