31,838 research outputs found
Crystal orientation and thickness dependence of superconductivity on tetragonal FeSe1-x thin films
Superconductivity was recently found in the simple tetragonal FeSe structure.
Recent studies suggest that FeSe is unconventional, with the symmetry of the
superconducting pairing state still under debate. To tackle these problems,
clean single crystals and thin films are required. Here we report the
fabrication of superconducting beta-phase FeSe1-x thin films on different
substrates using a pulsed laser deposition (PLD) technique. Quite
interestingly, the crystal orientation, and thus, superconductivity in these
thin films is sensitive to the growth temperature. At 320C, films grow
preferably along c-axis, but the onset of superconductivity depends on film
thickness. At 500C, films grow along (101), with little thickness dependence.
These results suggest that the low temperature structural deformation
previously found is crucial to the superconductivity of this material
Resonant Tunneling through S- and U-shaped Graphene Nanoribbons
We theoretically investigate resonant tunneling through S- and U-shaped
nanostructured graphene nanoribbons. A rich structure of resonant tunneling
peaks are found eminating from different quasi-bound states in the middle
region. The tunneling current can be turned on and off by varying the Fermi
energy. Tunability of resonant tunneling is realized by changing the width of
the left and/or right leads and without the use of any external gates.Comment: 6 pages, 7 figure
Production of the -Wave Excited -States through the Boson Decays
In Ref.[7],we have dealt with the production of the two color-singlet
-wave -quarkonium states and
through the boson decays. As an
important sequential work, we make a further discussion on the production of
the more complicated -wave excited -quarkonium states, i.e.
and (with
). More over, we also calculate the channel with the two color-octet
quarkonium states and , whose contributions to the decay width maybe at the same order of
magnitude as that of the color-singlet -wave states according to the naive
nonrelativistic quantum chromodynamics scaling rules. The -wave states shall
provide sizable contributions to the production, whose decay width is
about 20% of the total decay width . After summing up all
the mentioned -quarkonium states' contributions, we obtain
KeV, where the errors are caused
by the main uncertainty sources.Comment: 8 pages, 5 figures and 2 tables. basic formulae in the appendix are
cut off to match the published version, which can be found in v1. to be
published in Eur.Phys.J.
Valley-dependent Brewster angles and Goos-Hanchen effect in strained graphene
We demonstrate theoretically how local strains in graphene can be tailored to
generate a valley polarized current. By suitable engineering of local strain
profiles, we find that electrons in opposite valleys (K or K') show different
Brewster-like angles and Goos-H\"anchen shifts, exhibiting a close analogy with
light propagating behavior. In a strain-induced waveguide, electrons in K and
K' valleys have different group velocities, which can be used to construct a
valley filter in graphene without the need for any external fields.Comment: 5 pages, 4 figure
Three-Dimensional Modelling and Simulation of the Ice Accretion Process on Aircraft Wings
© 2018 Chang S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.In this article, a new computational method for the three-dimensional (3D) ice accretion analysis on an aircraft wing is formulated and validated. The two-phase flow field is calculated based on Eulerian-Eulerian approach using standard dispersed turbulence model and second order upwind differencing with the aid of commercial software Fluent, and the corresponding local droplet collection efficiency, convective heat transfer coefficient, freezing fraction and surface temperature are obtained. The classical Messinger model is modified to be capable of describing 3D thermodynamic characteristics of ice accretion. Considering effects of runback water, which is along chordwise and spanwise direction, an extended Messinger method is employed for the prediction of the 3D ice accretion rates. Validation of the newly developed model is carried out through comparisons with available experimental ice shape and LEWICE codes over a GLC-305 wing under both rime and glaze icing conditions. Results show that good agreement is achieved between the current computational ice shapes and the compared results. Further calculations based on the proposed method over a M6 wing under different test conditions are numerically demonstrated.Peer reviewedFinal Published versio
Boson Decays to Meson and Its Uncertainties
The programming new collider with high luminosity shall provide
another useful platform to study the properties of the doubly heavy meson
in addition to the hadronic colliders as LHC and TEVATRON. Under the `New Trace
Amplitude Approach', we calculate the production of the spin-singlet and
the spin-triplet mesons through the boson decays, where
uncertainties for the production are also discussed. Our results show
KeV and
KeV, where the errors are caused by
varying and within their reasonable regions.Comment: 11 pages, 5 figures, 2 tables. To be published in Eur.Phys.J.
Ultraviolet photonic crystal laser
We fabricated two dimensional photonic crystal structures in zinc oxide films
with focused ion beam etching. Lasing is realized in the near ultraviolet
frequency at room temperature under optical pumping. From the measurement of
lasing frequency and spatial profile of the lasing modes, as well as the
photonic band structure calculation, we conclude that lasing occurs in the
strongly localized defect modes near the edges of photonic band gap. These
defect modes originate from the structure disorder unintentionally introduced
during the fabrication process.Comment: 4 pages, 4 figure
The NLO QCD Corrections to Meson Production in Decays
The decay width of to meson is evaluated at the next-to-leading
order(NLO) accuracy in strong interaction. Numerical calculation shows that the
NLO correction to this process is remarkable. The quantum
chromodynamics(QCD)renormalization scale dependence of the results is obviously
depressed, and hence the uncertainties lying in the leading order calculation
are reduced.Comment: 14 pages, 7 figures; references added; expressions and typos ammende
Structure of the Partition Function and Transfer Matrices for the Potts Model in a Magnetic Field on Lattice Strips
We determine the general structure of the partition function of the -state
Potts model in an external magnetic field, for arbitrary ,
temperature variable , and magnetic field variable , on cyclic, M\"obius,
and free strip graphs of the square (sq), triangular (tri), and honeycomb
(hc) lattices with width and arbitrarily great length . For the
cyclic case we prove that the partition function has the form ,
where denotes the lattice type, are specified
polynomials of degree in , is the corresponding
transfer matrix, and () for ,
respectively. An analogous formula is given for M\"obius strips, while only
appears for free strips. We exhibit a method for
calculating for arbitrary and give illustrative
examples. Explicit results for arbitrary are presented for
with and . We find very simple formulas
for the determinant . We also give results for
self-dual cyclic strips of the square lattice.Comment: Reference added to a relevant paper by F. Y. W
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