1,089 research outputs found
Anomalous Josephson effect in d-wave superconductor junctions on TI surface
We study Josephson effect of -wave superconductor (DS)/ferromagnet
insulator(FI)/DS junctions on a surface of topological insulator (TI). We
calculate Josephson current for various orientations
of the junctions where is the macroscopic phase difference between
two DSs. In certain configurations, we find anomalous current-phase relation
with periodicity. In the
case where the first order Josephson coupling is absent without magnetization
in FI, can be proportional to . The magnitude of the
obtained Josephson current is enhanced due to the zero energy states on the
edge of DS on TI. Even if we introduce an -wave component of pair potential
in DS, we can still expect the anomalous current-phase relation in asymmetric
DS junctions with . This can be used to probe
the induced -wave component of pair potential on TI surface in high-
cuperate/TI hybrid structures.Comment: 6 pages, 4 figure
Microscopic theory of tunneling spectroscopy in SrRuO
We study the surface Andreev bound state (ABS) of superconducting
SrRuO, which is a candidate material for the realization of the chiral
-wave superconducting state. In order to clarify the role of chiral edge
modes as ABSs, the surface density of states and the tunneling conductance is
calculated in the normal metal/SrRuO junction within the framework of
recursive Green's function method, while taking into account the orbital
degrees of freedom (including Spin-Orbit interactions) with realistic material
parameters. In SrRuO, there are two bands and
originating from quasi-one-dimensional orbitals and and a
two-dimensional band originating from orbital. We discuss
about the contributions of various electronic bands to LDOS and the influence
of atomic spin-orbit interaction (SOI). In the light of our calculations,
quasi-one-dimensional model with dominant pair potentials in and
bands is consistent with conductance measurements in
Au/SrRuO junctions.Comment: to be published in J. Phys. Soc. Jpn., 10 pages, 12 figure
Josephson effect in a multi-orbital model for SrRuO
We study Josephson current between s-wave/spin-triplet superconductor
junctions by taking into account details of band structures in
SrRuO such as three conduction bands, spin-orbit interaction in the
bulk and that at the interface. We assume five superconducting order parameters
in SrRuO: a chiral p-wave symmetry and four helical p-wave
symmetries. We calculate current-phase relationship in these
junctions, where is the macroscopic phase difference between two
superconductors. The results for a chiral p-wave pairing symmetry show that
term appears in the current-phase relation due to time-reversal
symmetry (TRS) breaking. On the other hand, term is absent in
the helical pairing states which preserve the TRS. We also study the dependence
of maximum Josephson current on an external magnetic flux in a
corner junction. The calculated results of show a relation
in a chiral state and
in a helical state. We calculate in a
corner and a symmetric SQUIDs geometry. In a symmetric SQUID geometry, the
relation is satisfied for all the pairing states and
it is impossible to distinguish chiral state from helical one. On the other
hand, results for a corner SQUID always show
and for a chiral and a helical states, respectively.
Experimental tests of these relations in a corner junctions and SQUIDs may
serve as a tool for unambiguous determination of the pairing symmetry in
SrRuO
How Has Intervention Fidelity Been Assessed in Smoking Cessation Interventions? A Systematic Review
Introduction. Intervention fidelity concerns the degree to which interventions are implemented as intended. Fidelity frameworks propose fidelity is a multidimensional concept relevant at intervention designer, provider, and recipient levels; yet the extent to which it is assessed multidimensionally is unclear. Smoking cessation interventions are complex, including multiple components, often delivered over multiple sessions and/or at scale in clinical practice; this increases susceptibility variation in the fidelity with which they are delivered. This review examined the extent to which five dimensions from the Behaviour Change Consortium fidelity framework (design, training, delivery, receipt, and enactment) were assessed in fidelity assessments of smoking cessation interventions (randomised control trials (RCTs)). Methods. Five electronic databases were searched using terms "smoking cessation,""interventions,""fidelity,"and "randomised control trials."Eligible studies included RCTs of smoking cessation behavioural interventions, published post 2006 after publication of the framework, reporting assessment of fidelity. The data extraction form was structured around the framework, which specifies a number of items regarding assessment and reporting of each dimension. Data extraction included study characteristics, dimensions assessed, data collection, and analysis strategies. A score per dimension was calculated, indicating its presence. Results. 55 studies were reviewed. There was a wide variability in data collection approaches used to assess fidelity. Fidelity of delivery was the most commonly assessed and linked to the intervention outcomes (73% of the studies). Fidelity of enactment scored the highest according to the framework (average of 92.7%), and fidelity of training scored the lowest (average of 37.1%). Only a quarter of studies linked fidelity data to outcomes (27%). Conclusion. There is wide variability in methodological and analytical approaches that precludes comparison and synthesis. In order to realise the potential of fidelity investigations to increase scientific confidence in the interpretation of observed trial outcomes, studies should include analyses of the association between fidelity data and outcomes. Findings have highlighted recommendations for improving fidelity evaluations and reporting practices
Formal Total Synthesis of the Algal Toxin (−)-Polycavernoside A
A concise and largely catalysis-based approach to the potent algal toxin polycavernoside A (1) is described that intercepts a late-stage intermediate of a previous total synthesis; from there on, this challenging target can be reached in a small number of steps. Key to success was a sequence of a molybdenum-catalyzed ring-closing alkyne metathesis (RCAM) reaction to forge the macrocyclic frame, followed by a gold-catalyzed and strictly regioselective transannular hydroalkoxylation of the resulting cycloalkyne that allows the intricate oxygenation pattern of the macrolactone ring of 1 to be properly set. The required cyclization precursor 5 was assembled by the arguably most advanced fragment coupling process based on an Evans–Tishchenko redox esterification known to date, which was optimized to the extent that the precious coupling partners could be used in an almost equimolar ratio (6/7 1:1.3). The preparation of these building blocks features, inter alia, the power of the Sc(OTf)3-catalyzed Leighton crotylation as well as the superb selectivities of alkene cross metathesis, asymmetric keto-ester hydrogenation, and the Jacobsen epoxidation/epoxide resolution technologies
s-wave Superconductivity due to Suhl-Kondo Mechanism in NaCoOHO: Effect of Coulomb Interaction and Trigonal Distortion
To study the electron-phonon mechanism of superconductivity in NaxCoO2, we
perform semiquantitative analysis of the electron-phonon interaction (EPI)
between relevant optical phonons (breathing and shear phonons) and t_{2g}
electrons (a_{1g} and e_g' electrons) in the presence of trigonal distortion.
We consider two kinds of contributions to the EPI; the EPI originating from the
Coulomb potential of O ions and that originating from the d-p transfer integral
between Co and O in CoO_6 octahedron. We find that the EPI for shear phonons,
which induces the interorbital hopping of electrons, is large in NaxCoO_2
because of the trigonal distortion of CoO_2 layer. For this reason, Tc for
s-wave pairing is prominently enlarged owing to interorbital hopping of Cooper
pairs induced by shear phonons, even if the top of e_g' electron band is close
to but below the Fermi level as suggested experimentally. This mechanism of
superconductivity is referred to as the valence-band Suhl-Kondo (SK) mechanism.
Since the SK mechanism is seldom damaged by the Coulomb repulsion, s-wave
superconductivity is realized irrespective of large Coulomb interaction U~5 eV
at Co sites. We also study the oxygen isotope effect on Tc, and find that it
becomes very small due to strong Coulomb interaction. Finally, we discuss the
possible mechanism of anisotropic s-wave superconducting state in NaxCoO2,
resulting from the coexistence of strong EPI and the antiferromagnetic
fluctuations.Comment: 17 page
The Josephson current in Fe-based superconducting junctions: theory and experiment
We present theory of dc Josephson effect in contacts between Fe-based and
spin-singlet -wave superconductors. The method is based on the calculation
of temperature Green's function in the junction within the tight-binding model.
We calculate the phase dependencies of the Josephson current for different
orientations of the junction relative to the crystallographic axes of Fe-based
superconductor. Further, we consider the dependence of the Josephson current on
the thickness of an insulating layer and on temperature. Experimental data for
PbIn/BaK(FeAs) point-contact Josephson junctions are
consistent with theoretical predictions for symmetry of an order
parameter in this material. The proposed method can be further applied to
calculations of the dc Josephson current in contacts with other new
unconventional multiorbital superconductors, such as and
superconducting topological insulator .Comment: 16 pages, 14 figure
Effect of chloroquine chemoprophylaxis during pregnancy on birth weight : results of a randomized trial
- …