3,739 research outputs found
Long sandwich modules for photon veto detectors
Long lead-scintillator sandwich modules developed for the BNL experiment
KOPIO are described. The individual 4 m long module consists of 15 layers of 7
mm thick extruded scintillator and 15 layers of 1 mm lead absorber. Readout is
implemented via WLS fibers glued into grooves in a scintillator with 7 mm
spacing and viewed from both ends by the phototubes. Time resolution of 300 ps
for cosmic MIPs was obtained. Light output stability monitored for 2 years
shows no degradation beyond the measurement errors. A 4 m long C-bent sandwich
module was also manufactured and tested.Comment: 14 pages, 13 figures, 1 tabl
Helical vortex phase in the non-centrosymmetric CePt_3Si
We consider the role of magnetic fields on the broken inversion
superconductor CePt_3Si. We show that upper critical field for a field along
the c-axis exhibits a much weaker paramagnetic effect than for a field applied
perpendicular to the c-axis. The in-plane paramagnetic effect is strongly
reduced by the appearance of helical structure in the order parameter. We find
that to get good agreement between theory and recent experimental measurements
of H_{c2}, this helical structure is required. We propose a Josephson junction
experiment that can be used to detect this helical order. In particular, we
predict that Josephson current will exhibit a magnetic interference pattern for
a magnetic field applied perpendicular to the junction normal. We also discuss
unusual magnetic effects associated with the helical order.Comment: 5 pages, 2 figures, Accepted as Phys Rev. Lette
Observation of vortex coalescence in the anisotropic spin-triplet superconductor SrRuO
We present direct imaging of magnetic flux structures in the anisotropic,
spin-triplet superconductor SrRuO using a scanning SQUID
microscope. Individual quantized vortices were seen at low magnetic fields.
Coalescing vortices forming flux domains were revealed at intermediate fields.
Based on our observations we suggest that a mechanism intrinsic to the material
stabilizes the flux domains against the repulsive vortex-vortex interaction.
Topological defects like domain walls can provide this, implying proof for
unconventional chiral superconductivity.Comment: submitted to PR
Cooper Pairs with Broken Time-Reversal, Parity, and Spin-Rotational Symmetries in Singlet Type-II Superconductors
We show that singlet superconductivity in the Abrikosov vortex phase is
absolutely unstable with respect to the appearance of a chiral triplet
component of a superconducting order parameter. This chiral component, p_x + i
p_y, breaks time-reversal, parity, and spin rotational symmetries of the
internal order parameter, responsible for a relative motion of two electrons in
the Cooper pair. We demonstrate that the symmetry breaking Pauli paramagnetic
effects can be tuned by a magnetic field strength and direction and can be made
of the order of unity in organic and high-temperature layered superconductors.Comment: Submitted to Physical Review Letters on May 9th 200
A note on the extension of the polar decomposition for the multidimensional Burgers equation
It is shown that the generalizations to more than one space dimension of the
pole decomposition for the Burgers equation with finite viscosity and no force
are of the form u = -2 viscosity grad log P, where the P's are explicitly known
algebraic (or trigonometric) polynomials in the space variables with polynomial
(or exponential) dependence on time. Such solutions have polar singularities on
complex algebraic varieties.Comment: 3 pages; minor formatting and typos corrected. Submitted to Phys.
Rev. E (Rapid Comm.
Magnetic properties of superconductors with strong spin-orbit coupling
We study the response of a superconductor with a strong spin-orbit coupling
on an external magnetic field. The Ginzburg-Landau free energy functional is
derived microscopically for a general crystal structure, both with and without
an inversion center, and for an arbitrary symmetry of the superconducting order
parameter. As a by-product, we obtain the general expressions for the intrinsic
magnetic moment of the Cooper pairs. It is shown that the Ginzburg-Landau
gradient energy in a superconductor lacking inversion symmetry has unusual
structure. The general formalism is illustrated using as an example CePtSi,
which is the first known heavy-fermion superconductor without an inversion
center.Comment: Published version, 14 pages, minor correction
- …