251 research outputs found
Are There Nuclear Structure Effects on the Isoscalar Giant Monopole Resonance and Nuclear Incompressibility near A~90?
"Background-free" spectra of inelastic -particle scattering have been
measured at a beam energy of 385 MeV in Zr and Mo at
extremely forward angles, including 0. The ISGMR strength
distributions for the three nuclei coincide with each other, establishing
clearly that nuclear incompressibility is not influenced by nuclear shell
structure near 90 as was claimed in recent measurements.Comment: 5 pages, 4 figures; accepted for publication in Phys. Lett.
Generic First Order Orientation Transition of Vortex Lattices in Type II Superconductors
First order transition of vortex lattices (VL) observed in various
superconductors with four-fold symmetry is explained microscopically by
quasi-classical Eilenberger theory combined with nonlocal London theory. This
transition is intrinsic in the generic successive VL phase transition due to
either gap or Fermi velocity anisotropies. This is also suggested by the
electronic states around vortices. Ultimate origin of this phenomenon is
attributed to some what hidden frustrations of a spontaneous symmetry broken
hexagonal VL on the underlying four-fold crystalline symmetry.Comment: 4 pages, 5 figures, some typos are correcte
Nonlocal Effects and Shrinkage of the Vortex Core Radius in YNi2B2C Probed by muSR
The magnetic field distribution in the vortex state of YNi2B2C has been
probed by muon spin rotation (muSR). The analysis based on the London model
with nonlocal corrections shows that the vortex lattice has changed from
hexagonal to square with increasing magnetic field H. At low fields the vortex
core radius, rho_v(H), decreases with increasing H much steeper than what is
expected from the sqrt(H) behavior of the Sommerfeld constant gamma(H),
strongly suggesting that the anomaly in gamma(H) primarily arises from the
quasiparticle excitations outside the vortex cores.Comment: 4 pages, 4 figures, submitted to Phys. Rev.
Time-Reversal Symmetry-Breaking Superconductivity in Heavy Fermion PrOs4Sb12 detected by Muon Spin Relaxation
We report on muon spin relaxation measurements of the 4f^2-based
heavy-fermion superconductor filled-skutterudite PrOs4Sb12. The results reveal
the spontaneous appearance of static internal magnetic fields below the
superconducting transition temperature, providing unambiguous evidence for the
breaking of time-reversal symmetry in the superconducting state. A discussion
is made on which of the spin or orbital component of Cooper pairs carries a
nonzero momentum.Comment: 5 pages with 3 figure
Isoscalar Giant Monopole, Dipole, and Quadrupole Resonances in Zr and Mo
The isoscalar giant monopole, dipole, and quadrupole strength distributions
have been deduced in Zr, and Mo from "background-free"
spectra of inelastic -particle scattering at a beam energy of 385 MeV
at extremely forward angles, including 0. These strength
distributions were extracted by a multipole-decomposition analysis based on the
expected angular distributions of the respective multipoles. All these strength
distributions for the three nuclei practically coincide with each other,
affirming that giant resonances, being collective phenomena, are not influenced
by nuclear shell structure near 90, contrary to the claim in a recent
measurement.Comment: 12 pages, 12 figures; Accepted for publication in Phys. Rev. C. arXiv
admin note: text overlap with arXiv:1607.0219
Antiferromagnetic order and dielectric gap within the vortex core of antiferromagnetic superconductor
The structure of a superconducting vortex has been studied theoretically for
a dirty antiferromagnetic superconductor (AFSC), modelling an AFSC as a doped
semi-metal with s-wave superconducting pairing and antiferromagnetic
(dielectric) interaction between electrons (holes). It is also supposed that
the quasiparticles dispersion law possesses the property of nesting. The
distribution of the superconducting and magnetic order parameters near the
vortex core is calculated. It is shown that the antiferromagnetic order, been
suppressed at large distances, is restored around the superconducting flux and
the vortex core is in fact insulating and antiferromagnetic, in stark contrast
to the normal metal cores of traditional superconductors. Moreover, our model
calculations predict that as the temperature decreases the flux region of the
superconductivity and antiferromagnetism coexistence increases.Comment: 9 pages, 3 Postscript figures,NATO Advanced Research Workshop on
"Vortex dynamics in superconductors and other complex systems" Yalta, Crimea,
Ukraine, 13-17 September 200
On the Spin Gap Phase in lambda-(BETS)_2GaX_zY_{4-z}
The nature of the insulating ground state in quasi-two-dimensional organic
conductor lambda-(BETS)_2GaX_zY_{4-z}, where the existence of a spin gap is
suggested by susceptibility measurement, has been studied theoretically.
Hartree-Fock calculations at absolute zero temperature show that if the on-site
Coulomb interaction exceeds some critical value, then antiferromagnetic spin
ordering emerges and eventually leads to an insulating state which can be
considered as a two-dimensional localized spin system. Based on the quantum
Monte Carlo simulations of Katoh and Imada, we will show that this system
locates near the boundary between the antiferromagnetic phase and the spin gap
phase, so that experimental facts can be explained.Comment: 7 pages, 4 figure
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