18,607 research outputs found
Electronic Structures of Antiperovskite Superconductor MgCNi and Related Compounds
Electronic structure of a newly discovered antiperovskite superconductor
MgCNi is investigated by using the LMTO band method. The main contribution
to the density of states (DOS) at the Fermi energy comes from Ni
3 states which are hybridized with C 2 states. The DOS at is
varied substantially by the hole or electron doping due to the very high and
narrow DOS peak located just below . We have also explored
electronic structures of C-site and Mg-site doped MgCNi systems, and
described the superconductivity in terms of the conventional phonon mechanism.Comment: 3 pages, presented at ORBITAL2001 September 11-14, 2001 (Sendai,
JAPAN
Electronic structures of antiperovskite superconductors: MgXNi (X=B,C,N)
We have investigated electronic structures of a newly discovered
antiperovskite superconductor MgCNi and related compounds MgBNi and
MgNNi. In MgCNi, a peak of very narrow and high density of states is
located just below , which corresponds to the antibonding
state of Ni-3d and C- but with the predominant Ni-3d character. The
prominent nesting feature is observed in the -centered electron Fermi
surface of an octahedron-cage-like shape that originates from the 19th band.
The estimated superconducting parameters based on the simple rigid-ion
approximation are in reasonable agreement with experiment, suggesting that the
superconductivity in MgCNi is described well by the conventional phonon
mechanism.Comment: 5 pages, 5 figure
Fashion Conversation Data on Instagram
The fashion industry is establishing its presence on a number of
visual-centric social media like Instagram. This creates an interesting clash
as fashion brands that have traditionally practiced highly creative and
editorialized image marketing now have to engage with people on the platform
that epitomizes impromptu, realtime conversation. What kinds of fashion images
do brands and individuals share and what are the types of visual features that
attract likes and comments? In this research, we take both quantitative and
qualitative approaches to answer these questions. We analyze visual features of
fashion posts first via manual tagging and then via training on convolutional
neural networks. The classified images were examined across four types of
fashion brands: mega couture, small couture, designers, and high street. We
find that while product-only images make up the majority of fashion
conversation in terms of volume, body snaps and face images that portray
fashion items more naturally tend to receive a larger number of likes and
comments by the audience. Our findings bring insights into building an
automated tool for classifying or generating influential fashion information.
We make our novel dataset of {24,752} labeled images on fashion conversations,
containing visual and textual cues, available for the research community.Comment: 10 pages, 6 figures, This paper will be presented at ICWSM'1
Electronic structure of metallic antiperovskite compound GaCMn
We have investigated electronic structures of antiperovskite GaCMn and
related Mn compounds SnCMn, ZnCMn, and ZnNMn. In the paramagnetic
state of GaCMn, the Fermi surface nesting feature along the
direction is observed, which induces the antiferromagnetic (AFM) spin ordering
with the nesting vector {\bf Q} . Calculated
susceptibilities confirm the nesting scenario for GaCMn and also explain
various magnetic structures of other antiperovskite compounds. Through the band
folding effect, the AFM phase of GaCMn is stabilized. Nearly equal
densities of states at the Fermi level in the ferromagnetic and AFM phases of
GaCMn indicate that two phases are competing in the ground state.Comment: 4 pages, 5 figure
The Physical Significance of Singularities in the Chern--Simons Fermi Liquid Description of a Partially Filled Landau Level
We analyze the linear response of a half filled Landau level to long
wavelength and low frequency driving forces, using Fermi liquid theory for
composite fermions. This response is determined by the composite fermions
quasi--particle effective mass, , and quasi--particle Landau interaction
function . Analyzing infra--red divergences of perturbation
theory, we get an exact expression for , and conjecture the form of the
. We then conclude that in the limit of infinite cyclotron
frequency, and small , the composite fermion excitation
spectrum is continuous for , with
an unknown number. For fractional quantum Hall states near a half
filled Landau level, we derive an exact expression for the energy gap.Comment: 4 pages, RevTeX. This paper, being short and non-technical, could
serve as a useful starting point for reading our manuscript cond-mat/9502032.
The present paper does, however, include results not published in the forme
Thermal activation energy of 3D vortex matter in NaFe1-xCoxAs (x=0.01, 0.03 and 0.07) single crystals
We report on the thermally activated flux flow dependency on the doping
dependent mixed state in NaFe1-xCoxAs (x=0.01, 0.03, and 0.07) crystals using
the magnetoresistivity in the case of B//c-axis and B//ab-plane. It was found
clearly that irrespective of the doping ratio, magnetoresistivity showed a
distinct tail just above the Tc, offset associated with the thermally activated
flux flow (TAFF) in our crystals. Furthermore, in TAFF region the temperature
dependence of the activation energy follows the relation U(T, B)=U_0 (B)
(1-T/T_c )^q with q=1.5 in all studied crystals. The magnetic field dependence
of the activation energy follows a power law of U_0 (B)~B^(-{\alpha}) where the
exponent {\alpha} is changed from a low value to a high value at a crossover
field of B=~2T, indicating the transition from collective to plastic pinning in
the crystals. Finally, it is suggested that the 3D vortex phase is the dominant
phase in the low-temperature region as compared to the TAFF region in our
series samples
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