3,378 research outputs found
Thermodynamic and transport properties of underdoped cuprates from ARPES data
he relationship between photoemission spectra of high-
cuprates and their thermodynamic and transport properties are discussed. The
doping dependence of the expected quasi-particle density at the Fermi level
() are compared with the electronic specific heat coefficient
and that of the spectral weight at with the in-plane
and out-of-plane superfluid density. We have estimated the electrical
resistivity of underdoped cuprates from the momentum distribution curve (MDC)
at in the nodal direction. The temperature dependence of the MDC
width is also consistent with that of the electrical resistivity.Comment: 14 pages, 4 figures, proceeding of International Symposium on
Synchrotron Radiatin Research for Spin and Electronic States in d and f
Electron Systems(SRSES2003
Unexpected Dirac-Node Arc in the Topological Line-Node Semimetal HfSiS
We have performed angle-resolved photoemission spectroscopy on HfSiS, which
has been predicted to be a topological line-node semimetal with square Si
lattice. We found a quasi-two-dimensional Fermi surface hosting bulk nodal
lines, alongside the surface states at the Brillouin-zone corner exhibiting a
sizable Rashba splitting and band-mass renormalization due to many-body
interactions. Most notably, we discovered an unexpected Dirac-like dispersion
extending one-dimensionally in k space - the Dirac-node arc - near the bulk
node at the zone diagonal. These novel Dirac states reside on the surface and
could be related to hybridizations of bulk states, but currently we have no
explanation for its origin. This discovery poses an intriguing challenge to the
theoretical understanding of topological line-node semimetals.Comment: 5 pages, 4 figures (paper proper) + 2 pages, figures (supplemental
material
Zn-impurity effects on quasi-particle scattering in La2-xSrxCuO4 studied by angle-resolved photoemission spectroscopy
Angle-resolved photoemission measurements were performed on Zn-doped
La2-xSrxCuO4 (LSCO) to investigate the effects of Zn impurities on the low
energy electronic structure. The Zn-impurity-induced increase in the
quasi-particle (QP) width in momentum distribution curves (MDC) is
approximately isotropic on the entire Fermi surface and energy-independent near
the Fermi level (EF). The increase in the MDC width is consistent with the
increase in the residual resistivity due to the Zn impurities if we assume the
carrier number to be 1-x for x=0.17 and the Zn impurity to be a potential
scatterer close to the unitarity limit. For x=0.03, the residual resistivity is
found to be higher than that expected from the MDC width, and the effects of
antifferomagnetic fluctuations induced around the Zn impurities are discussed.
The leading edges of the spectra near (pi,0) for x=0.17 are shifted toward
higher energies relative to EF with Zn substitution, indicating a reduction of
the superconducting gap.Comment: 7 pages, 7 figure
Quantum Hall Effect on the Hofstadter Butterfly
Motivated by recent experimental attempts to detect the Hofstadter butterfly,
we numerically calculate the Hall conductivity in a modulated two-dimensional
electron system with disorder in the quantum Hall regime. We identify the
critical energies where the states are extended for each of butterfly subbands,
and obtain the trajectory as a function of the disorder. Remarkably, we find
that when the modulation becomes anisotropic, the critical energy branches
accompanying a change of the Hall conductivity.Comment: 4 pages, 6 figure
Natural fiber for green technology in automotive industry: a brief review
Fiber reinforced polymeric composites have been known and widely used because of their high specific strength and modulus compared to metals. In the last few years, biomaterials listed as a demand technology to be exploring by researchers especially in industrial purpose. This is push by environmental awareness and the over use of petrol resources lead to the development of new materials, called biocomposites, which will maintain a better future. This paper will be discussing about a brief review of natural fibers, use in automotive industry to achieve a green technology target in manufacturing of cars specifically. It's a fact that, related to weight reduction, the automotive industry can take advantages of using these materials, not only because of extinction of oil reserve, but because of high ability and importance of these materials itself in automobiles. Currently, most composites in the market are focused with long-term durability design while using nondegradable polymeric resins such as epoxies and high-strength fiber such as glass. All these materials prove to be a good characteristic of composite but still lack in environmental concern. This polymer and fiber are derived from petroleum, a nonreplenishable commodity. The momentum is to use biocomposites in common plastics to improve performance. Since the main purpose of this paper is to show a bio-composite which is suitable to replace the existing interior of automotive design, the work has focused on obtaining that bio-composite, taking account into the raw-materials cost reduction and the maintenance of the manufacturing process based on current scenario. The automotive industry is in their way to expand green technology in composites because the need is greatest. But producing the composites is energy intensive and polluting, while the durability of conventional composites, often seen as an advantage, is also their biggest challenge. Current fibers use in industry right now is difficult to dispose. They do not degrade naturally and could linger for generations
Novel anisotropy in the superconducting gap structure of Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} probed by quasiparticle heat transport
Since the nature of pairing interactions is manifested in the superconducting
gap symmetry, the exact gap structure, particularly any deviation from the
simple d_{x^2-y^2} symmetry, would help elucidating the pairing mechanism in
high-T_c cuprates. Anisotropic heat transport measurement in
Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} (Bi-2212) reveals that the quasiparticle
populations are different for the two nodal directions and thus the gap
structure must be uniquely anisotropic, suggesting that pairing is governed by
interactions with a rather complicated anisotropy. Intriguingly, it is found
that the "plateau" in the magnetic-field dependence of the thermal conductivity
is observed only in the b-axis transport.Comment: 4 pages, 5 figures, accepted for publication in Phys. Rev. Let
Asymmetric neutrino emission due to neutrino-nucleon scatterings in supernova magnetic fields
We derive the cross section of neutrino-nucleon scatterings in supernova
magnetic fields, including weak-magnetism and recoil corrections. Since the
weak interaction violates the parity, the scattering cross section
asymmetrically depends on the directions of the neutrino momenta to the
magnetic field; the origin of pulsar kicks may be explained by the mechanism.
An asymmetric neutrino emission (a drift flux) due to neutrino-nucleon
scatterings is absent at the leading level of , where
is the nucleon magneton, is the magnetic field strength, and is
the matter temperature at a neutrinosphere. This is because at this level the
drift flux of the neutrinos are exactly canceled by that of the antineutrinos.
Hence, the relevant asymmetry in the neutrino emission is suppressed by much
smaller coefficient of , where is the nucleon mass;
detailed form of the relevant drift flux is also derived from the scattering
cross section, using a simple diffusion approximation. It appears that the
asymmetric neutrino emission is too small to induce the observed pulsar kicks.
However, we note the fact that the drift flux is proportional to the deviation
of the neutrino distribution function from the value of thermal equilibrium at
neutrinosphere. Since the deviation can be large for non-electron neutrinos, it
is expected that there occurs cancellation between the deviation and the small
suppression factor of . Using a simple parameterization,
we show that the drift flux due to neutrino-nucleon scatterings may be
comparable to the leading term due to beta processes with nucleons, which has
been estimated to give a relevant kick velocity when the magnetic field is
sufficiently strong as -- G.Comment: 19 pages, 1 figure. Accepted by Physical Review
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