6,309 research outputs found
Magnetotransport Study of the Canted Antiferromagnetic Phase in Bilayer Quantum Hall State
Magnetotransport properties are investigated in the bilayer quantum Hall
state at the total filling factor . We measured the activation energy
elaborately as a function of the total electron density and the density
difference between the two layers. Our experimental data demonstrate clearly
the emergence of the canted antiferromagnetic (CAF) phase between the
ferromagnetic phase and the spin-singlet phase. The stability of the CAF phase
is discussed by the comparison between experimental results and theoretical
calculations using a Hartree-Fock approximation and an exact diagonalization
study. The data reveal also an intrinsic structure of the CAF phase divided
into two regions according to the dominancy between the intralayer and
interlayer correlations.Comment: 6 pages, 7 figure
Interlayer Coherence in the and Bilayer Quantum Hall States
We have measured the Hall-plateau width and the activation energy of the
bilayer quantum Hall (BLQH) states at the Landau-level filling factor
and 2 by tilting the sample and simultaneously changing the electron density in
each quantum well. The phase transition between the commensurate and
incommensurate states are confirmed at and discovered at . In
particular, three different BLQH states are identified; the compound
state, the coherent commensurate state, and the coherent incommensurate state.Comment: 4 pages including 5 figure
Microscopic Theory of Skyrmions in Quantum Hall Ferromagnets
We present a microscopic theory of skyrmions in the monolayer quantum Hall
ferromagnet. It is a peculiar feature of the system that the number density and
the spin density are entangled intrinsically as dictated by the W
algebra. The skyrmion and antiskyrmion states are constructed as W-rotated states of the hole-excited and electron-excited states,
respectively. They are spin textures accompanied with density modulation that
decreases the Coulomb energy. We calculate their excitation energy as a
function of the Zeeman gap and compared the result with experimental data.Comment: 15 pages (to be published in PRB
Syntactic View of Sigma-Tau Generation of Permutations
We give a syntactic view of the Sawada-Williams -generation of
permutations. The corresponding sequence of -operations, of length
is shown to be highly compressible: it has bit
description. Using this compact description we design fast algorithms for
ranking and unranking permutations.Comment: accepted on LATA201
A Local One-Zone Model of MHD Turbulence in Dwarf Nova Disks
The evolution of the magnetorotational instability (MRI) during the
transition from outburst to quiescence in a dwarf nova disk is investigated
using three-dimensional MHD simulations. The shearing box approximation is
adopted for the analysis, so that the efficiency of angular momentum transport
is studied in a small local patch of the disk: this is usually referred as to a
one-zone model. To take account of the low ionization fraction of the disk, the
induction equation includes both ohmic dissipation and the Hall effect. We
induce a transition from outburst to quiescence by an instantaneous decrease of
the temperature. The evolution of the MRI during the transition is found to be
very sensitive to the temperature of the quiescent disk. As long as the
temperature is higher than a critical value of about 2000 K, MHD turbulence and
angular momentum transport is sustained by the MRI. However, MHD turbulence
dies away within an orbital time if the temperature falls below this critical
value. In this case, the stress drops off by more than 2 orders of magnitude,
and is dominated by the Reynolds stress associated with the remnant motions
from the outburst. The critical temperature depends slightly on the distance
from the central star and the local density of the disk.Comment: 20 pages, 2 tables, 6 figures, accepted for publication in Ap
Skyrmion pseudoSkyrmion Transition in Bilayer Quantum Hall States at
Bilayer quantum Hall states at have been demonstrated to possess a
distinguished state with interlayer phase coherence. The state has both
excitations of Skyrmion with spin and pseudoSkyrmion with pseudospin. We show
that Skyrmion pseudoSkyrmion transition arises in the state
by changing imbalance between electron densities in both layers; PseudoSkyrmion
is realized at balance point, while Skyrmion is realized at large imbalance.
The transition can be seen by observing the dependence of activation energies
on magnetic field parallel to the layers.Comment: 12 pages, no figure
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
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
Liquefaction Analysis of a Petroleum Tank-Ground-Pile Ring System in Reclaimed Ground Near Seashore
In this paper, liquefaction analysis (LIQCA2D, LIQCA3D) of a petroleum tank-ground-foundation system is conducted using a dynamic finite element-finite difference method. The nonlinearity of the ground is simulated with a kinematic hardening elastoplastic model, which has been verified by a series of hollow cylindrical torsional shear tests and been proved that it can well predict the behaviors of soils such as the liquefaction strength curve, the stress-strain relation as well as the effective stress paths during cyclic loading. In the numerical analyses, an FEM-DEM analytical method is adopted to the soil-water coupled analysis. The petroleum tank is built on a reclaimed ground and is near to seashore. In order to enhance the seismic strength of the tank-soil system, a ring-shaped steel pile wall is designed for the tank. At first, two-dimensional (2-D) and three-dimensional (3-D) finite element analyses are conducted for the tank without the remediation method to identify the difference between 2-D and 3-D analyses. Then, a 3-D dynamic analysis is conducted for the tank in two different cases, that is, with and without the remediation. The mu-nose of the research is to evaluate numerically the effectiveness of the remediation method when a tank is built on a potentially liquefied ground
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