676 research outputs found
Three-orbital study on the orbital distillation effect in the high Tc cuprates
Our recent study has revealed that the mixture of the dz2 orbital component
into the Fermi surface suppresses Tc in the cuprates such as La2CuO4. We have
also shown that applying hydrostatic pressure enhances Tc due to smaller mixing
of the Cu4s component. We call these the "orbital distillation" effect. In our
previous study, the 4s orbital was taken into account through the hoppings in
the dx2-y2 sector, but here we consider a model in which of the dx2-y2, dz2 and
4s orbitals are all considered explicitly. The present study reinforces our
conclusion that smaller 4s hybridization further enhances Tc.Comment: 4 pages, 2 figures, submitted as a proceeding of ISS2012(Tokyo
Multiorbital analysis of the effects of uniaxial and hydrostatic pressure on in the single-layered cuprate superconductors
The origin of uniaxial and hydrostatic pressure effects on in the
single-layered cuprate superconductors is theoretically explored. A two-orbital
model, derived from first principles and analyzed with the fluctuation exchange
approximation gives axial-dependent pressure coefficients, , , with a hydrostatic response
for both La214 and Hg1201 cuprates, in qualitative
agreement with experiments. Physically, this is shown to come from a unified
picture in which higher is achieved with an "orbital distillation",
namely, the less the main band is hybridized with the
and orbitals higher the . Some implications for obtaining higher
materials are discussed.Comment: 6pages, 4 figure
Theoretical study of the chemical pressure effect on Tc in the cuprate superconductors
Application of physical pressure on the cuprate superconductors often results in an enhancement of Tc. Motivated by this fact, we study the chemical pressure effect on the single-layered La2CuO4 and HgBa2CuO4 starting from the two-orbital Hubbard model deduced from a first-principles calculation. It is shown that the chemical pressure effects induced by La-site substitution in La2CuO4 or Hg-site substitution in HgBa2CuO4 are not expected to be effective for raising Tc
Three-orbital study on the orbital distillation effect in the high Tc cuprates
Our recent study has revealed that the mixture of the dz2 orbital component into the Fermi surface suppresses Tc in the cuprates such as La2CuO4. We have also shown that applying hydrostatic pressure enhances Tc due to smaller mixing of the Cu4s component. We call these the “orbital distillation” effect. In our previous study, the 4s orbital was taken into account through the hoppings in the dx2-y2 sector, but here we consider a model in which of the dx2-y2, dz2 and 4s orbitals are all considered explicitly. The present study reinforces our conclusion that smaller 4s hybridization further enhances Tc
Sensitivity of the superconducting state and magnetic susceptibility to key aspects of electronic structure in ferropnictides
Experiments on the iron-pnictide superconductors appear to show some
materials where the ground state is fully gapped, and others where low-energy
excitations dominate, possibly indicative of gap nodes. Within the framework of
a 5-orbital spin fluctuation theory for these systems, we discuss how changes
in the doping, the electronic structure or interaction parameters can tune the
system from a fully gapped to nodal sign-changing gap with s-wave ()
symmetry (). In particular we focus on the role of the hole pocket at
the point of the unfolded Brillouin zone identified as crucial to
the pairing by Kuroki {\it et al.}, and show that its presence leads to
additional nesting of hole and electron pockets which stabilizes the isotropic
state. The pocket's contribution to the pairing can be tuned by doping,
surface effects, and by changes in interaction parameters, which we examine.
Analytic expressions for orbital pairing vertices calculated within the RPA
fluctuation exchange approximation allow us to draw connections between aspects
of electronic structure, interaction parameters, and the form of the
superconducting gap
A Twisted Ladder: relating the Fe superconductors to the high cuprates
We construct a 2-leg ladder model of an Fe-pnictide superconductor and
discuss its properties and relationship with the familiar 2-leg cuprate model.
Our results suggest that the underlying pairing mechanism for the Fe-pnictide
superconductors is similar to that for the cuprates.Comment: 5 pages, 4 figure
Phylogenetic groups and cephalosporin resistance genes of Escherichia coli from diseased food-producing animals in Japan
A total of 318 Escherichia coli isolates obtained from different food-producing animals affected with colibacillosis between 2001 and 2006 were subjected to phylogenetic analysis: 72 bovine isolates, 89 poultry isolates and 157 porcine isolates. Overall, the phylogenetic group A was predominant in isolates from cattle (36/72, 50%) and pigs (101/157, 64.3%) whereas groups A (44/89, 49.4%) and D (40/89, 44.9%) were predominant in isolates from poultry. In addition, group B2 was not found among diseased food-producing animals except for a poultry isolate. Thus, the phylogenetic group distribution of E. coli from diseased animals was different by animal species. Among the 318 isolates, cefazolin resistance (minimum inhibitory concentrations: ≥32 μg/ml) was found in six bovine isolates, 29 poultry isolates and three porcine isolates. Of them, 11 isolates (nine from poultry and two from cattle) produced extended spectrum β-lactamase (ESBL). The two bovine isolates produced blaCTX-M-2, while the nine poultry isolates produced blaCTX-M-25 (4), blaSHV-2 (3), blaCTX-M-15 (1) and blaCTX-M-2 (1). Thus, our results showed that several types of ESBL were identified and three types of β-lactamase (SHV-2, CTX-M-25 and CTX-M-15) were observed for the first time in E. coli from diseased animals in Japan
Nuclear magnetic relaxation and superfluid density in Fe-pnictide superconductors: An anisotropic \pm s-wave scenario
We discuss the nuclear magnetic relaxation rate and the superfluid density
with the use of the effective five-band model by Kuroki et al. [Phys. Rev.
Lett. 101, 087004 (2008)] in Fe-based superconductors. We show that a
fully-gapped anisotropic \pm s-wave superconductivity consistently explains
experimental observations. In our phenomenological model, the gaps are assumed
to be anisotropic on the electron-like \beta Fermi surfaces around the M point,
where the maximum of the anisotropic gap is about four times larger than the
minimum.Comment: 10 pages, 8 figures; Submitted versio
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Turning Males On: Activation of Male Courtship Behavior in Drosophila melanogaster
The innate sexual behaviors of Drosophila melanogaster males are an attractive system for elucidating how complex behavior patterns are generated. The potential for male sexual behavior in D. melanogaster is specified by the fruitless (fru) and doublesex (dsx) sex regulatory genes. We used the temperature-sensitive activator dTRPA1 to probe the roles of fruM- and dsx-expressing neurons in male courtship behaviors. Almost all steps of courtship, from courtship song to ejaculation, can be induced at very high levels through activation of either all fruM or all dsx neurons in solitary males. Detailed characterizations reveal different roles for fruM and dsx in male courtship. Surprisingly, the system for mate discrimination still works well when all dsx neurons are activated, but is impaired when all fruM neurons are activated. Most strikingly, we provide evidence for a fruM-independent courtship pathway that is primarily vision dependent
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