868 research outputs found
Local density of states and superconducting gap in the iron chalcogenide superconductor FeSeTe observed by scanning tunneling spectroscopy
We report on the first investigation of the quasiparticle local density of
states and superconducting gap in the iron chalcogenide superconductor
FeSeTe ( K). The surface of
a cleaved crystal revealed an atomic square lattice, superimposed on the
inhomogeneous background, with a lattice constant of \AA without any
reconstruction. Tunneling spectra measured at 4.2 K exhibit the superconducting
gap, which completely disappears at 18 K, with a magnitude of meV,
corresponding to .In stark contrast
to the cuprate superconductors, the value of the observed superconducting gap
is relatively homogeneous, following a sharp distribution with a small standard
deviation of 0.23 meV. Conversely, the normal-state local density of states
observed above shows spatial variation over a wide energy
range of more than 1 eV, probably due to the excess iron present in the
crystal.Comment: 4 pages, 5 figure
On Kinetic Theory Viscosity in a Rotating Gas
Clarke and Pringle (2004) derived a proper viscosity formula in a rotating
gas by applying mean free path theory. We study their argument in detail and
show that their result can be derived with a much simpler calculational
procedure and physically clearer picture.Comment: 7 pages, 1 figure; Prog. Theor. Phys. Vol. 112, No.
Local Measurement of Microwave Response with Local Tunneling Spectra Using Near Field Microwave Microscopy
We have designed and built a near-field scanning microwave microscope, which
has been used to measure the local microwave response and the local
density-of-states (LDOS) in the area including the boundary between the gold
deposited and the non-deposited region on highly-orientated pyrolytic graphite
at a frequency of about 7.3 GHz. We have succeeded in measuring the spatial
variation of both the LDOS and the surface resistance. It can be observed that
the surface resistance in gold deposited region with the metallic tunneling
spectra is smaller than that in the non-deposited region with the U-shaped
tunneling spectra.Comment: 3 pages, 3 figures
Effect of Side Chain Length on Segregation of Squalane between Smectic Layers Formed by Rod-Like Polysilanes
The segregation of spherical molecules (squalane) between the smectic layers of rod-like polymers (polysilanes) with narrow molecular weight distributions were investigated by synchrotron radiation small-angle X-ray scattering (SR-SAXS), atomic force microscopy (AFM) observations, and molecular dynamics simulations to elucidate the effect of the polymer side chain length on the segregation. It has been theoretically predicted that the smectic phase of the rod-like particles will be stabilized by inserting the spherical particles into the interstitial region between the smectic layers when the diameter of the spherical particles is smaller than that of the rod-like particles whose length is sufficiently long. We found that the segregation of squalane was unaffected by the molecular weight (Mw) of the polysilane in the range of 9,200-44,100 g/mol, and the diameter of the polysilane showed the optimal size of 5.64 nm for the segregation of squalane whose diameter is 6.57 nm although the origin of these inconsistencies between theory and experiment is currently not clear
Threshold corrections to the radiative breaking of electroweak symmetry and neutralino dark matter in supersymmetric seesaw model
We study the radiative electroweak symmetry breaking and the relic abundance
of neutralino dark matter in the supersymmetric type I seesaw model. In this
model, there exist threshold corrections to Higgs bilinear terms coming from
heavy singlet sneutrino loops, which make the soft supersymmetry breaking (SSB)
mass for up-type Higgs shift at the seesaw scale and thus a minimization
condition for the Higgs potential is affected. We show that the required
fine-tuning between the Higgsino mass parameter mu and the SSB mass for up-type
Higgs may be reduced at the electroweak scale, due to the threshold
corrections. We also present how the parameter mu depends on the SSB
B-parameter for heavy singlet sneutrinos. Since the property of neutralino dark
matter is quite sensitive to the size of mu, we discuss how the relic abundance
of neutralino dark matter is affected by the SSB B-parameter. Taking the SSB
B-parameter of order of a few hundreds TeV, the required relic abundance of
neutralino dark matter can be correctly achieved. In this case, dark matter is
a mixture of bino and Higgsino, under the condition that gaugino masses are
universal at the grand unification scale.Comment: 27 pages, 3 figures; references added, discussion about RGEs added,
the version published on PR
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