544 research outputs found
Effect of Band Structure on the Symmetry of Superconducting States
Effects of the band structure on the symmetry of superconducting (SC) states
are studied. For a square lattice system with a nearest-neighbor attractive
interaction, SC states with various symmetries are found by changing the band
structure, or, the shape of the Fermi surface. The spin-triplet (-wave) and spin-singlet (- or s-wave) SC states, and states with their
coexistence (, ) can be stabilized within the same type of
interaction. The stability of interlayer-pairing states with line nodes is also
examined, and its relation to the SC state of SrRuO is discussed.Comment: 4 pages, 4 figure
The Mixed State of Charge-Density-Wave in a Ring-Shaped Single Crystals
Charge-density-wave (CDW) phase transition in a ring-shaped crystals,
recently synthesized by Tanda et al. [Nature, 417, 397 (2002)], is studied
based on a mean-field-approximation of Ginzburg-Landau free energy. It is shown
that in a ring-shaped crystals CDW undergoes frustration due to the curvature
(bending) of the ring (geometrical frustration) and, thus, forms a mixed state
analogous to what a type-II superconductor forms under a magnetic field. We
discuss the nature of the phase transition in the ring-CDW in relation to
recent experiments.Comment: 6 pages, 4 figure
Forming method and characteristics of coiled spring in small coil diameter and with high rectangular ratio in winding wire cross section
This paper presents a new forming method of a coiled spring which is used as a forceps manipulator of a surgical robot. Joint parts of forceps manipulator are required to be “easy to bend and strong to twist”. This demand is fulfilled by using coiled springs with high rectangular ratio in winding wire cross section. However, the coiled springs are conventionally expensive as they are fabricated by machining. This study proposed a new and inexpensive forming method for fabrication of the coiled spring with high rectangular ratio in the wire cross section. In this method, the coiled spring with circular shape in the winding wire cross section is compressed in the coil axial direction by upsetting, and then the rectangle ratio of the wire becomes high. The coiled spring with a high rectangular ratio of 3 was obtained by the proposed method. In addition, a numerical analysis and an experiment were conducted for evaluation of the formed coiled springs in terms of tensile, torsional, and bending characteristics. The formed coiled springs were easy to bend and strong to twist from results. Moreover, the elastic limit of the formed coiled springs improved due to work hardening by upsetting
Shallow and diffuse spin-orbit potential for proton elastic scattering from neutron-rich helium isotopes at 71 MeV/nucleon
Vector analyzing powers for proton elastic scattering from 8He at 71
MeV/nucleon have been measured using a solid polarized proton target operated
in a low magnetic field of 0.1 T. The spin-orbit potential obtained from a
phenomenological optical model analysis is found to be significantly shallower
and more diffuse than the global systematics of stable nuclei, which is an
indication that the spin-orbit potential is modified for scattering involving
neutron-rich nuclei. A close similarity between the matter radius and the
root-mean-square radius of the spin-orbit potential is also identified.Comment: 6 pages, 4 figures, accepted for publication in Physical Review C
Rapid Communicatio
Ground state of an distorted diamond chain - model of
We study the ground state of the model Hamiltonian of the trimerized
quantum Heisenberg chain in which
the non-magnetic ground state is observed recently. This model consists of
stacked trimers and has three kinds of coupling constants between spins; the
intra-trimer coupling constant and the inter-trimer coupling constants
and . All of these constants are assumed to be antiferromagnetic. By
use of the analytical method and physical considerations, we show that there
are three phases on the plane (, ), the dimer phase, the spin fluid phase
and the ferrimagnetic phase. The dimer phase is caused by the frustration
effect. In the dimer phase, there exists the excitation gap between the
two-fold degenerate ground state and the first excited state, which explains
the non-magnetic ground state observed in . We also obtain the phase diagram on the
plane from the numerical diagonalization data for finite systems by use of the
Lanczos algorithm.Comment: LaTeX2e, 15 pages, 21 eps figures, typos corrected, slightly detailed
explanation adde
Phase diagram and critical properties of the frustrated Kondo necklace model in a magnetic field
The critical properties of the frustrated Kondo necklace model with a half
saturation magnetization () have been studied by means of an
exact-diagonalization method. It is shown from bosonization technique that the
model can be effectively expressed as a quantum sine-Gordom model. Thus it may
show three (dimer plateau, N{\'e}el plateau and Tomonaga-Luttinger liquid)
phases due to competitions among the Ising anisotropy , and the
nearest- and next-nearest-neighbor exchange interactions and . The
boundary lines on the phase diagram separating the three
phases are determined by the method of level spectroscopy based on the
conformal field theory.Comment: 5 pages, 5 figure
Performance of the neutron polarimeter NPOL3 for high resolution measurements
We describe the neutron polarimeter NPOL3 for the measurement of polarization
transfer observables with a typical high resolution of 300 keV
at 200 MeV.
The NPOL3 system consists of three planes of neutron detectors.
The first two planes for neutron polarization analysis are made of 20 sets of
one-dimensional position-sensitive plastic scintillation counters with a size
of 100 cm 10 cm 5 cm, and they cover the area of 100
100 .
The last plane for detecting doubly scattered neutrons or recoiled protons is
made of the two-dimensional position-sensitive liquid scintillation counter
with a size of 100 cm 100 cm 10 cm.
The effective analyzing powers and double scattering
efficiencies were measured by using the three kinds
of polarized neutrons from the , , and reactions at = 198 MeV.
The performance of NPOL3 defined as
are similar to that of the
Indiana Neutron POLarimeter (INPOL) by taking into account for the counter
configuration difference between these two neutron polarimeters.Comment: 28 pages, 18 figures, submitted to Nucl. Instrum. Methods Phys. Res.
Geometrically Frustrated Crystals: Elastic Theory and Dislocations
Elastic theory of ring-(or cylinder-)shaped crystals is constructed and the
generation of edge dislocations due to geometrical frustration caused by the
bending is studied. The analogy to superconducting (or superfluid) vortex state
is pointed out and the phase diagram of the ring-crystal, which depends on
radius and thickness, is discussed.Comment: 4 pages, 3 figure
Precision measurement of vector and tensor analyzing powers in elastic deuteron-proton scattering
High precision vector and tensor analyzing powers of elastic deuteron-proton
d+p scattering have been measured at intermediate energies to investigate
effects of three-nucleon forces (3NF). Angular distribution in the range of
70-120 degree in the center-of mass frame for incident-deuteron energies of 130
and 180 MeV were obtained using the RIKEN facility. The beam polarization was
unambiguously determined by measuring the 12C(d,alpha)10B(2+) reaction at 0
degree. Results of the measurements are compared with state-of-the-art
three-nucleon calculations. The present modeling of nucleon-nucleon forces and
its extension to the three-nucleon system is not sufficient to describe the
high precision data consistently and requires, therefore, further
investigation
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