1,373 research outputs found
Two-Band-Type Superconducting Instability in MgB2
Using the tight-binding method for the -bands in MgB, the Hubbard
on-site Coulomb interaction on two inequivalent boron -orbitals is
transformed into expressions in terms of -band operators. For scattering
processes relevant to the problemin which a wave vector {\bf q} is parallel to
, it is found to take a relatively simple form consisting of
intra-band Coulomb scattering, interband pair scattering etc. with large
constant coupling constants. This allows to get a simple expression for the
amplitude of interband pair scattering between two -bands, which diverges
if the interband polarization function in it becomes large enough.The latter
was approximately evaluated and found to be largely enhanced in the band
structure in MgB. These results lead to a divergent interband pair
scattering, meaning two-band-type superconducting instability with enhanced
. Adding a subsidiary BCS attractive interaction in each band into
consideration, a semi-quantitative gap equation is given, and and isotope
exponent are derived. The present instability is asserted to be the
origin of high in MgB.Comment: 4 pages, to be published in J. Phys. Soc. Jpn. vol. 70, No.
Superconductivity Driven by the Interband Coulomb Interaction and Implications for the Superconducting Mechanism of MgB2
Superconducting mechanism mediated by interband exchange Coulomb repulsion is
examined in an extended two-band Hubbard models with a wide band crossing the
Fermi level and coexisting with a narrower band located at moderately lower
energy. We apply newly developed path-integral renormalization group method to
reliably calculate pairing correlations. The correlation shows marked
enhancement at moderate amplitudes of the exchange Coulomb repulsion taken
smaller than the on-site repulsion for the narrower band. The pairing symmetry
is s-wave while it has unconventional phases with the opposite sign between the
order parameters on the two bands, in agreement with the mean-field prediction.
Since the band structure of recently discovered superconductor MgB shares
basic similarities with our model, we propose that the present results provide
a relevant clue for the understanding of the superconducting mechanism in
MgB as well as in this class of multi-band materials with good metallic
conduction in the normal state.Comment: 4pages, 2figure
Decrosslinking enables visualization of RNA-guided endonuclease-in situ labeling signals for DNA sequences in plant tissues
Information about the positioning of individual loci in the nucleus and the status of epigenetic modifications at these loci in each cell contained in plant tissue increases our understanding of how cells in a tissue coordinate gene expression. To obtain such information, a less damaging method of visualizing DNA in tissue that can be used with immunohistochemistry is required. Recently, a less damaging DNA visualization method using the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/associated caspase 9) system, named RNA-guided endonuclease-in situ labeling (RGEN-ISL), was reported. This system made it possible to visualize a target DNA locus in a nucleus fixed on a glass slide with a set of simple operations, but it could not be applied to cells in plant tissues. In this work, we have developed a modified RGEN-ISL method with decrosslinking that made it possible to simultaneously detect the DNA loci and immunohistochemistry signals, including histone modification, in various types of plant tissues and species
Sign reversals of the Quantum Hall Effect in quasi-1D conductors
The sign reversals of the Quantum Hall Effect observed in
quasi-one-dimensional conductors of the Bechgaard salts family are explained
within the framework of the quantized nesting model. The sequence of reversals
is driven by slight modifications of the geometry of the Fermi surface. It is
explained why only even phases can have signign reversals and why negative
phases are less stable than positive ones.Comment: 4 LaTex pages, 3 Postscript figure
Ground state of the three-band Hubbard model
The ground state of the two-dimensional three-band Hubbard model in oxide
superconductors is investigated by using the variational Monte Carlo method.
The Gutzwiller-projected BCS and spin- density wave (SDW) functions are
employed in the search for a possible ground state with respect to dependences
on electron density. Antiferromagnetic correlations are considerably enhanced
near half-filling. It is shown that the d-wave state may exist away from
half-filling for both the hole and electron doping cases. The overall structure
of the phase diagram obtained by the calculations qualitatively agrees with
experimental indications. The superconducting condensation energy is in
reasonable agreement with the experimental value obtained from specific heat
and critical magnetic field measurements for optimally doped samples. The
inhomogeneous SDW state is also examined near 1/8-hole doping.Comment: 10 pages, 17 figure
Unconventional charge density wave in the organic conductor alpha-(BEDT-TTF)_2KHg(SCN)_4
The low temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4 salt is known
for its surprising angular dependent magnetoresistance (ADMR), which has been
studied intensively in the last decade. However, the nature of the LTP has not
been understood until now. Here we analyse theoretically ADMR in unconventional
(or nodal) charge density wave (UCDW). In magnetic field the quasiparticle
spectrum in UCDW is quantized, which gives rise to spectacular ADMR. The
present model accounts for many striking features of ADMR data in
alpha-(BEDT-TTF)_2KHg(SCN)_4.Comment: 5 pages, 6 figure
High Accuracy and Automatic Measurement of the Pattern Linewidth on Very Large Scale Integrated Circuits
High accuracy measurement of pattern linewidth is particularly important in Very Large Scale Integrated Circuits (VLSI) manufacturing.
The measurement of pattern linewidth has been done by optical methods. However, the optical methods have several problems: as the measured value depends on slope angle at pattern edge, thickness and optical property of film and also substrate, there exists a large difference in size (0.3 μm) between the defined edge and the true edge in case of photoresist linewidth measurements. Especially, the optical methods have severe problems to measure bottom of pattern edge and are unsuitable to measure pattern linewidth in VLSI\u27s manufacturing.
The secondary electron signal obtained by electron beam irradiation can be used to measure pattern linewidth with high accuracy. In order to avoid radiation damage and contamination during in-process measurement, low primary electron energy (1 keV) and low dosage of primary electrons (1X1020electrons/cm2) are used.
As secondary electron signal includes much random noise, signal averaging and smoothing methods for random noise reduction are utilized.
The automatic detection of bottom edge from secondary electron profile is achieved by detecting the increasing point of line profile which corresponds to the cross point of the average line and the slope line.
The linewidths obtained by this method agree with the linewidths calculated from the pattern pitch of cross section image obtained by scanning electron microscopy(SEM) within the error of 0.04μm
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