238 research outputs found
Ginzburg-Landau Theory for a p-Wave Sr_2RuO_4 Superconductor: Vortex Core Structure and Extended London Theory
Based on a two dimensional odd-parity superconducting order parameter for
Sr_2RuO_4 with p-wave symmetry, we investigate the single vortex and vortex
lattice structure of the mixed phase near H_{c1}. Ginzburg-Landau calculations
for a single vortex show a fourfold structure with an orientation depending on
the microscopic Fermi surface properties. The corresponding extended London
theory is developed to determine the vortex lattice structure and we find near
H_{c1} a centered rectangular vortex lattice. As the field is increased from
H_{c1} this lattice continuously deforms until a square vortex lattice is
achieved. In the centered rectangular phase the field distribution, as
measurable through \mu-SR experiments, exhibits a characteristic two peak
structure (similar to that predicted in high temperature and borocarbide
superconductors).Comment: 12 pages, 7 figure
Josephson effect in point contacts between ''f-wave'' superconductors
A stationary Josephson effect in point contacts between triplet
superconductors is analyzed theoretically for most probable models of the order
parameter in UPt_{3} and Sr_{2}RuO_{4}. The consequence of misorientation of
crystals in superconducting banks on this effect is considered. We show that
different models for the order parameter lead to quite different current-phase
dependences. For certain angles of misorientation a boundary between
superconductors can generate the parallel to surface spontaneous current. In a
number of cases the state with a zero Josephson current and minimum of the free
energy corresponds to a spontaneous phase difference. This phase difference
depends on the misorientation angle and may possess any value. We conclude that
experimental investigations of the current-phase dependences of small junctions
can be used for determination of the order parameter symmetry in the mentioned
above superconductors.Comment: 11 pages, 8 figure
Low-temperature structural model of hcp solid C
We report intermolecular potential-energy calculations for solid C_ and
determine the optimum static orientations of the molecules at low temperature;
we find them to be consistent with the monoclinic structural model proposed by
us in an earlier report [Solid State Commun. {\bf 105), 247 (1998)]. This model
indicates that the C_5 axis of the molecule is tilted by an angle 18^o
from the monoclinic b axis in contrast with the molecular orientation proposed
by Verheijen {\it et al.} [J. Chem. Phys. {\bf 166}, 287 (1992)] where the C_5
axis is parallel to the monoclinic b axis. In this calculation we have
incorporated the effective bond charge Coulomb potential together with the
Lennard-Jones potential between the molecule at the origin of the monoclinic
unit cell and its six nearest neighbours, three above and three below. The
minimum energy configuration for the molecular orientations turns out to be at
=18^o, =8^o, and =5^o, where , , and
define the molecular orientations.Comment: ReVTeX (4 pages) + 2 PostScript figure
Half-quantum vortex and d-soliton in SrRuO
Assuming that the superconductivity in SrRuO is described by a planar
p-wave order parameter, we consider possible topological defects in
SrRuO. In particular, it is shown that both of the -soliton
and half-quantum vortex can be created in the presence of the magnetic field
parallel to the - plane. We discuss how one can detect the -soliton and half-quantum vortex experimentally.Comment: 8 pages, 3 figure
Identifying the pairing symmetry in the Sr2RuO4 superconductor
We have analyzed heat capacity and thermal conductivity measurements of
Sr2RuO4 in the normal and superconducting state and come to the conclusion that
an order parameter with nodal lines on the Fermi surface is required to account
for the observed low-temperature behavior. A gapped order parameter is
inconsistent with the reported thermodynamic and transport data. Guided by a
strongly peaked dynamical susceptibility along the diagonals of the Brillouin
zone in neutron scattering data, we suggest a spin-fluctuation mechanism that
would favor the pairing state with the gap maxima along the zone diagonals
(such as for a d_{xy} gap). The most plausible candidates are an odd parity,
spin-triplet, f-wave pairing state, or an even parity, spin-singlet, d-wave
state. Based on our analysis of possible pairing functions we propose
measurements of the ultrasound attenuation and thermal conductivity in the
magnetic field to further constrain the list of possible pairing states.Comment: 7 pages, 5 figures; updated list of references and extended
introduction; to appear in Phys. Rev. B (Oct. 2000
Sound localization with bilateral bone conduction devices
Purpose To investigate sound localization in patients bilaterally fitted with bone conduction devices (BCDs). Additionally, clinically applicable methods to improve localization accuracy were explored. Methods Fifteen adults with bilaterally fitted percutaneous BCDs were included. At baseline, sound localization, (un)aided pure-tone thresholds, device use, speech, spatial and qualities of hearing scale (SSQ) and York hearing-related quality of life (YHRQL) questionnaire were measured. Settings to optimize sound localizing were added to the BCDs. At 1 month, sound localization was assessed again and localization was practiced with a series of sounds with visual feedback. At 3 months, localization performance, device use and questionnaire scores were determined again. Results At baseline, one patient with congenital hearing loss demonstrated near excellent localization performance and four other patients (three with congenital hearing loss) localized sounds (quite) accurately. Seven patients with acquired hearing loss were able to lateralize sounds, i.e. identify whether sounds were coming from the left or right side, but could not localize sounds accurately. Three patients (one with congenital hearing loss) could not even lateralize sounds correctly. SSQ scores were significantly higher at 3 months. Localization performance, device use and YHRQL scores were not significantly different between visits. Conclusion In this study, the majority of experienced bilateral BCD users could lateralize sounds and one third was able to localize sounds (quite) accurately. The localization performance was robust and stable over time. Although SSQ scores were increased at the last visit, optimizing device settings and a short practice session did not improve sound localization
Mechanism of spin-triplet superconductivity in Sr2RuO4
The unique Fermi surfaces and their nesting properties of Sr2RuO4 are
considered. The existence of unconventional superconductivity is shown
microscopically, for the first time, from the magnetic interactions (due to
nesting) and the phonon-mediated interactions. The odd-parity superconductivity
is favored in the and sheets of the Fermi surface, and the
various superconductivities are possible in the sheet. There are a
number of possible odd-parity gaps, which include the gaps with nodes, the
breaking of time-reversal symmetry and .Comment: 4 pages, 3 figure
Influence of gap structures to specific heat in oriented magnetic fields: Application to the orbital dependent superconductor, SrRuO
We discuss influence of modulation of gap function and anisotropy of Fermi
velocity to field angle dependences of upper critical field, , and
specific heat, , on the basis of the approximate analytic solution in the
quasiclassical formalism. Using 4-fold modulation of the gap function and the
Fermi velocity in the single-band model, we demonstrate field and temperature
dependence of oscillatory amplitude of and . We apply the method to
the effective two-band model to discuss the gap structure of SrRuO,
focusing on recent field angle-resolved experiments. It is shown that the gap
structures with the intermediate magnitude of minima in direction for
band, and tiny minima of gaps in directions for and
bands give consistent behaviors with experiments. The interplay of the
above two gaps also explains the anomalous temperature dependence of in-plane
anisotropy, where the opposite contribution from the passive
band is pronounced near .Comment: 7 pages, 11 figures in JPSJ forma
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