1,170 research outputs found
Spontaneous mass current and textures of p-wave superfluids of trapped Fermionic atom gases at rest and under rotation
It is found theoretically based on the Ginzburg-Landau framework that p-wave
superfluids of neutral atom gases in three dimension harmonic traps exhibit
spontaneous mass current at rest, whose direction depends on trap geometry.
Under rotation various types of the order parameter textures are stabilized,
including Mermin-Ho and Anderson-Toulouse-Chechetkin vortices. In a cigar shape
trap spontaneous current flows longitudial to the rotation axis and thus
perpendicular to the ordinary rotational current. These features, spontaneous
mass current at rest and texture formation, can be used as diagnoses for p-wave
superfluidity.Comment: 5 pages, 5 figure
Local solutions in Sobolev spaces with negative indices for the "good" Boussinesq equation
We study the local well-posedness of the initial-value problem for the
nonlinear "good" Boussinesq equation with data in Sobolev spaces \textit{}
for negative indices of .Comment: Referee comments incorporate
Edge Current due to Majorana Fermions in Superfluid He A- and B-Phases
We propose a method utilizing edge current to observe Majorana fermions in
the surface Andreev bound state for the superfluid He A- and B-phases. The
proposal is based on self-consistent analytic solutions of quasi-classical
Green's function with an edge. The local density of states and edge mass
current in the A-phase or edge spin current in the B-phase can be obtained from
these solutions. The edge current carried by the Majorana fermions is partially
cancelled by quasiparticles (QPs) in the continuum state outside the superfluid
gap. QPs contributing to the edge current in the continuum state are
distributed in energy even away from the superfluid gap. The effect of Majorana
fermions emerges in the depletion of the edge current by temperature within a
low-temperature range. The observations that the reduction in the mass current
is changed by -power in the A-phase and the reduction in the spin current
is changed by -power in the B-phase establish the existence of Majorana
fermions. We also point out another possibility for observing Majorana fermions
by controlling surface roughness.Comment: 13 pages, 4 figures, published versio
Evidence for time-reversal symmetry breaking of the superconducting state near twin-boundary interfaces in FeSe
Junctions and interfaces consisting of unconventional superconductors provide
an excellent experimental playground to study exotic phenomena related to the
phase of the order parameter. Not only the complex structure of unconventional
order parameters have an impact on the Josephson effects, but also may
profoundly alter the quasi-particle excitation spectrum near a junction. Here,
by using spectroscopic-imaging scanning tunneling microscopy, we visualize the
spatial evolution of the local density of states (LDOS) near twin boundaries
(TBs) of the nodal superconductor FeSe. The rotation of the
crystallographic orientation across the TB twists the structure of the
unconventional order parameter, which may, in principle, bring about a
zero-energy LDOS peak at the TB. The LDOS at the TB observed in our study, in
contrast, does not exhibit any signature of a zero-energy peak and an apparent
gap amplitude remains finite all the way across the TB. The low-energy
quasiparticle excitations associated with the gap nodes are affected by the TB
over a distance more than an order of magnitude larger than the coherence
length . The modification of the low-energy states is even more
prominent in the region between two neighboring TBs separated by a distance
. In this region the spectral weight near the Fermi level
(0.2~meV) due to the nodal quasiparticle spectrum is almost
completely removed. These behaviors suggest that the TB induces a fully-gapped
state, invoking a possible twist of the order parameter structure which breaks
time-reversal symmetry.Comment: 12 pages, 6 figure
Genetic and Epigenetic Alterations of Lysophosphatidic Acid Receptor Genes in Rodent Tumors by Experimental Models
Lysophosphatidic acid (LPA) is a bioactive mediator and induces several
biological effects, including cell proliferation, migration, morphogenesis and
differentiation. LPA interacts with at least six G protein-coupled receptors
(GPCRs), including LPA receptor-1 (LPA1), LPA2,
LPA3, LPA4, LPA5 and LPA6. These
receptors show different biological functions through the binding of LPA,
depending on the type of cells. In human malignancies, a high level of LPA
production was found in plasma and ascites in ovarian cancer cases. Moreover,
aberrant expression levels of LPA receptor genes were detected in some cancer
cells. Therefore, it is suggested that LPA receptors may be involved in the
pathogenesis of tumor cells as well as LPA per se. Recently, we have reported
that alterations of LPA receptor genes also occur in rodent tumors. In this
review, we summarize the recent evidence in the investigations of LPA receptor
alterations in rodent tumors by experimental models
Singular Vortex in Narrow Cylinders of Superfluid 3He-A Phase
Motivated by the on-going rotating cryostat experiments in ISSP, Univ. of
Tokyo, we explore the textures and vortices in superfluid 3He-A phase confined
in narrow cylinders, whose radii are R=50mum and 115mum. The calculations are
based on the Ginzburg-Landau (GL) framework, which fully takes into account the
orbital (l-vector) and spin (d-vector) degrees of freedom for chiral p-wave
pairing superfluid. The GL free energy functional is solved numerically by
using best known GL parameters appropriate for the actual experimental
situations at P=3.2MPa and H=21.6mT. We identify the ground state l-vector
configuration as radial disgyration (RD) texture with the polar core both at
rest and low rotations and associated d-vector textures for both narrow
cylinder systems under high magnetic fields. The RD which has a singularity at
center, changes into Mermin-Ho texture above the critical rotation speed which
is determined precisely, providing an experimental check for own proposal.Comment: 22 pages, 12 figure
Fabrication of high quality plan-view TEM specimens using the focused ion beam
We describe a technique using a focused ion beam instrument to fabricate high quality plan-view specimens for transmission electron microscopy studies. The technique is simple, site-specific and is capable of fabricating multiple large, >100 μm2 electron transparent windows within epitaxially-grown thin films. A film of La0.67Sr0.33MnO3 is used to demonstrate the technique and its structural and functional properties are surveyed by high resolution imaging, electron spectroscopy, atomic force microscopy and Lorentz electron microscopy. The window is demonstrated to have good thickness uniformity and a low defect density that does not impair the film’s Curie temperature. The technique will enable the study of in–plane structural and functional properties of a variety of epitaxial thin film systems
Flat bands in topological media
Topological media are systems whose properties are protected by topology and
thus are robust to deformations of the system. In topological insulators and
superconductors the bulk-surface and bulk-vortex correspondence gives rise to
the gapless Weyl, Dirac or Majorana fermions on the surface of the system and
inside vortex cores. Here we show that in gapless topological media, the
bulk-surface and bulk-vortex correspondence is more effective: it produces
topologically protected gapless fermions without dispersion -- the flat band.
Fermion zero modes forming the flat band are localized on the surface of
topological media with protected nodal lines and in the vortex core in systems
with topologically protected Fermi points (Weyl points). Flat band has an
extremely singular density of states, and we show that this property may give
rise in particular to surface superconductivity which could exist even at room
temperature.Comment: 9 pages, 5 figures, version to appear in JETP Letter
Pressure induced high-spin to low-spin transition in FeS evidenced by x-ray emission spectroscopy
We report the observation of the pressure-induced high-spin to low-spin
transition in FeS using new high-pressure synchrotron x-ray emission
spectroscopy techniques. The transition is evidenced by the disappearance of
the low-energy satellite in the Fe K emission spectrum of FeS. Moreover,
the phase transition is reversible and closely related to the structural phase
transition from a manganese phosphide-like phase to a monoclinic phase. The
study opens new opportunities for investigating the electronic properties of
materials under pressure.Comment: ReVTeX, 4 pages, 3 figures inserted with epsfig. minor modifications
before submission to PR
Acoustic radiation controls friction: Evidence from a spring-block experiment
Brittle failures of materials and earthquakes generate acoustic/seismic waves
which lead to radiation damping feedbacks that should be introduced in the
dynamical equations of crack motion. We present direct experimental evidence of
the importance of this feedback on the acoustic noise spectrum of
well-controlled spring-block sliding experiments performed on a variety of
smooth surfaces. The full noise spectrum is quantitatively explained by a
simple noisy harmonic oscillator equation with a radiation damping force
proportional to the derivative of the acceleration, added to a standard viscous
term.Comment: 4 pages including 3 figures. Replaced with version accepted in PR
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