500 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
Ginzburg-Landau Equations for Coexistent States of Superconductivity and Antiferromagnetism in t-J model
Ginzburg-Landau (GL) equations for the coexistent state of superconductivity
and antiferromagnetism are derived microscopically from the t-J model with
extended transfer integrals. GL equations and the GL free energy, which are
obtained based on the slave-boson mean-field approximation, reflect the
electronic structure of the microscopic model, especially the evolution of the
Fermi surface due to the change of the doping rate. Thus they are suitable for
studying the material dependence of the coexistent states in high- cuprate
superconductors.Comment: 12 page
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
Microscopic derivation of Ginzburg-Landau equations for coexistent states of superconductivity and magnetism
Ginzburg-Landau (GL) equations for the coexistent states of superconductivity
and magnetism are derived microscopically from the extended Hubbard model with
on-site repulsive and nearest-neighbor attractive interactions. In the derived
GL free energy a cubic term that couples the spin-singlet and spin-triplet
components of superconducting order parameters (SCOP) with magnetization
exists. This term gives rise to a spin-triplet SCOP near the interface between
a spin-singlet superconductor and a ferromagnet, consistent with previous
theoretical studies based on the Bogoliubov de Gennes method and the
quasiclassical Green's function theory. In coexistent states of singlet
superconductivity and antiferromagnetism it leads to the occurrence of
pi-triplet SCOPs.Comment: 18 page
Domain-wall structure of a classical Heisenberg ferromagnet on a Mobius strip
We study theoretically the structure of domain walls in ferromagnetic states
on Mobius strips. A two-dimensional classical Heisenberg ferromagnet with
single-site anisotropy is treated within a mean-field approximation by taking
into account the boundary condition to realize the Mobius geometry. It is found
that two types of domain walls can be formed, namely, parallel or perpendicular
to the circumference, and that the relative stability of these domain walls is
sensitive to the change in temperature and an applied magnetic field. The
magnetization has a discontinuity as a function of temperature and the external
field.Comment: 7 pages, 10 figures; published versio
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
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.
Analyzing power for the proton elastic scattering from neutron-rich 6He nucleus
Vector analyzing power for the proton-6He elastic scattering at 71
MeV/nucleon has been measured for the first time, with a newly developed
polarized proton solid target working at low magnetic field of 0.09 T. The
results are found to be incompatible with a t-matrix folding model prediction.
Comparisons of the data with g-matrix folding analyses clearly show that the
vector analyzing power is sensitive to the nuclear structure model used in the
reaction analysis. The alpha-core distribution in 6He is suggested to be a
possible key to understand the nuclear structure sensitivity.Comment: 5 pages, 3 figures, accepted for publication as a Rapid Communication
in Physical Review
- …