919 research outputs found
Theory of Spin polarized Tunneling in Superconducting Sr2RuO4
A theory of tunneling conductance in ferromagnetic metal/insulator/triplet -
supercondcutor junctions is presented for unitary and non-unitary spin triplet
pairing states which are promising candidates for the superconducting paring
symmetry of Sr2RuO4. As the magnitude of the exchange interaction in the
ferromagnetic metal is increased, the conductance for the unitary pairing state
below the energy gap is reduced in contrast to the case for the non-unitary
pairing state
Electronic Properties of Topological Materials: Optical Excitations in Moebius Conjugated Polymers
Electronic structures and optical excitations in Moebius conjugated polymers
are studied theoretically. Periodic and Moebius boundary conditions are applied
to the tight binding model of poly(para-phenylene), taking exciton effects into
account. We discuss that oligomers with a few structural units are more
effective than polymers for observations of effects of discrete wave numbers
that are shifted by the change in boundary condition. Next, calculations of
optical absorption spectra are reported. Certain components of optical
absorption for an electric field perpendicular to the polymer axis mix with
absorption spectra for an electric field parallel to the polymer axis.
Therefore, the polarization dependences of an electric field of light enable us
to detect whether conjugated polymers have the Moebius boundary.Comment: 10 pages, 6 figures, to be published in J. Phys. Soc. Jpn., Vol. 74
No. 2 (February, 2005), Letter sectio
Theory of magnetotunneling spectroscopy in spin triplet p-wave superconductors
We study the influence of a magnetic field on the zero-bias conductance
peak (ZBCP) due to zero-energy Andreev bound state (ZES) in normal metal /
unconventional superconductor. For p-wave junctions, ZBCP does not split into
two by even for sufficiently low transparent junctions, where ZBCP clearly
splits for d-wave. This unique property originates from the fact that for
p-wave superconductors, perpendicularly injected quasiparticle form ZES, which
contribute most dominantly on the tunneling conductance. In addition, we show
that for +i-wave superconductor junctions, the height of ZBCP is
sensitive to due to the formation of broken time reversal symmetry state.
We propose that tunneling spectroscopy in the presence of magnetic field,
, , is an promising method to determine the pairing
symmetry of unconventional superconductors.Comment: 4 pages, 6 figures, using jpsj2.cl
VEGF(164)-mediated inflammation is required for pathological, but not physiological, ischemia-induced retinal neovascularization
Hypoxia-induced VEGF governs both physiological retinal vascular development and pathological retinal neovascularization. In the current paper, the mechanisms of physiological and pathological neovascularization are compared and contrasted. During pathological neovascularization, both the absolute and relative expression levels for VEGF(164) increased to a greater degree than during physiological neovascularization. Furthermore, extensive leukocyte adhesion was observed at the leading edge of pathological, but not physiological, neovascularization. When a VEGF(164)-specific neutralizing aptamer was administered, it potently suppressed the leukocyte adhesion and pathological neovascularization, whereas it had little or no effect on physiological neovascularization. In parallel experiments, genetically altered VEGF(164)-deficient (VEGF(120/188)) mice exhibited no difference in physiological neovascularization when compared with wild-type (VEGF(+/+)) controls. In contrast, administration of a VEGFk-1/Fc fusion protein, which blocks all VEGF isoforms, led to significant suppression of both pathological and physiological neovascularization. In addition, the targeted inactivation of monocyte lineage cells with clodronate-liposomes led to the suppression of pathological neovascularization. Conversely, the blockade of T lymphocyte-mediated immune responses with an anti-CD2 antibody exacerbated pathological neovascularization. These data highlight important molecular and cellular differences between physiological and pathological retinal neovascularization. During pathological neovascularization, VEGF(164) selectively induces inflammation and cellular immunity. These processes provide positive and negative angiogenic regulation, respectively. Together, new therapeutic approaches for selectively targeting pathological, but not physiological, retinal neovascularization are outlined
Tunneling current in triplet f-wave superconductors with horizontal lines of nodes
We calculate the tunneling conductance spectra of a
normal-metal/insulator/triplet superconductor using the
Blonder-Tinkham-Klapwijk (BTK) formulation. Possible states for the
superconductor are considered with horizontal lines of nodes, breaking the time
reversal symmetry. These results would be useful to discriminate between
pairing states in superonductor SrRuO and also in UPt.Comment: 12 pages, 7 figure
Temperature-dependence of spin-polarized transport in ferromagnet / unconventional superconductor junctions
Tunneling conductance in ferromagnet / unconventional superconductor
junctions is studied theoretically as a function of temperatures and
spin-polarization in feromagnets. In d-wave superconductor junctions, the
existence of a zero-energy Andreev bound state drastically affects the
temperature-dependence of the zero-bias conductance (ZBC). In p-wave triplet
superconductor junctions, numerical results show a wide variety in
temperature-dependence of the ZBC depending on the direction of the magnetic
moment in ferromagnets and the pairing symmetry in superconductors such as
, and -wave pair potential. The last one is a
promising symmetry of SrRuO. From these characteristic features in the
conductance, we may obtain the information about the degree of
spin-polarization in ferromagnets and the direction of the -vector in
triplet superconductors
Edge states and determination of pairing symmetry in superconducting Sr2RuO4
We calculate the energy dispersion of the surface Andreev states and their
contribution to tunneling conductance for the order parameters with horizontal
and vertical lines of nodes proposed for superconducting Sr2RuO4. For vertical
lines, we find double peaks in tunneling spectra reflecting the van Hove
singularities in the density of surface states originating from the turning
points in their energy dispersion. For horizontal lines, we find a single
cusp-like peak at zero bias, which agrees very well with the experimental data
on tunneling in Sr2RuO4.Comment: 6 pages, 6 figures. V.2: comparison with experiment added and
discussion of horizontal nodes expanded. v.3: significant expansion: 1 figure
and 2 pages added. v.4: acknowledgements added. Additional viewgraphs with
experimental and theoretical curves superimposed are available at
http://www2.physics.umd.edu/~yakovenk/talks/Sr2RuO4
Theory of tunneling spectroscopy in superconducting Sr2RuO4
A theory for tunneling spectroscopy in normal metal /insulator/triplet
superconductor junction is presented. We assume two kinds of non-unitary
triplet superconducting states which are the most promising states for
SrRuO. The calculated conductance spectra showzero-bias peaks as
well as gap structures. The existences of residual components in the spectra
reflect the non-unitary properties of superconducting states.Comment: 5pages, 4figures(included), to be published in Phys.Rev.B 56, (1997
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