15,110 research outputs found
SET based experiments for HTSC materials: II
The cuprates seem to exhibit statistics, dimensionality and phase transitions
in novel ways. The nature of excitations
[i.e. quasiparticle or collective], spin-charge separation, stripes [static
and dynamics], inhomogeneities, psuedogap, effect of impurity dopings [e.g. Zn,
Ni] and any other phenomenon in these materials must be consistently
understood. In this note we further discuss our original suggestion of using
Single Electron Tunneling Transistor
[SET] based experiments to understand the role of charge dynamics in these
systems. Assuming that SET operates as an efficient charge detection system we
can expect to understand the underlying physics of charge transport and charge
fluctuations in these materials for a range of doping. Experiments such as
these can be classed in a general sense as mesoscopic and nano characterization
of cuprates and related materials. In principle such experiments can show if
electron is fractionalized in cuprates as indicated by ARPES data. In contrast
to flux trapping experiments SET based experiments are more direct in providing
evidence about spin-charge separation. In addition a detailed picture of nano
charge dynamics in cuprates may be obtained.Comment: 10 pages revtex plus four figures; ICMAT 2001 Conference Symposium P:
P10-0
Parameters for Systems Exhibiting Local Lattice Distortions, Charge and Spin Ordering
Keeping in mind the experimental results that indicate local lattice
distortions, charge and spin orderings, we have developed a phenomenological
approach which allows us to describe the electronic phase diagram of cuprates
and related systems in terms of few parameters.In the present work we consider
a third-order parameter theory which characterize charge, spin and
superconductivity orderings. We are thus led to a theory of three scalar
fields. By coupling these scalars to gauge fields we are naturally led to
string-like solutions, which we interpret as stripes. This ties nicely with our
quantum group conjecture that 1d systems play an important role in the physics
of cuprates and related materials. We show that this simple approach can give
rough values for two-order parameters which can be naively be interpreted as
charge and spin orderings. We also report our attempt to understand how local
lattice distortions are involved and what role they play in terms of these two
order parameters.Comment: 8 pages revtex, Published in AIP Conference Proceedings 554: Int.
Sym. on Physics in Local Lattice Distortions, July 23-26, 200
Segregation in a fluidized binary granular mixture: Competition between buoyancy and geometric forces
Starting from the hydrodynamic equations of binary granular mixtures, we
derive an evolution equation for the relative velocity of the intruders, which
is shown to be coupled to the inertia of the smaller particles. The onset of
Brazil-nut segregation is explained as a competition between the buoyancy and
geometric forces: the Archimedean buoyancy force, a buoyancy force due to the
difference between the energies of two granular species, and two geometric
forces, one compressive and the other-one tensile in nature, due to the
size-difference. We show that inelastic dissipation strongly affects the phase
diagram of the Brazil nut phenomenon and our model is able to explain the
experimental results of Breu et al. (PRL, 2003, vol. 90, p. 01402).Comment: 5 pages, 2 figure
Can international alliances influence sustainable fashion practices: a UK/Bangladesh experience?
The presentation will outline current work that has been undertaken as part of a three-year British Council funded Development Partnerships in Higher Education (DelPHE) project that brings together international collaboration between London College of Fashion (LCF), the BGMEA Institute of Fashion Technology (BIFT) in Dhaka and the United Nations Industrial Development Organization (UNIDO). As retailers are increasingly under pressure to ensure that ethical and environmental standards run all the way through the supply chain, there is a need for research projects to explore best practice and ways forward to improve the competitiveness of the Bangladesh manufacturing sector to add value in this area
Thermal Photons and Lepton Pairs from Quark Gluon Plasma and Hot Hadronic Matter
The formulation of the real and virtual photon production rate from strongly
interacting matter is presented in the framework of finite temperature field
theory. The changes in the hadronic spectral function induced by temperature
are discussed within the ambit of the Walecka type model, gauged linear and
non-linear sigma models, hidden local symmetry approach and QCD sum rule
approach. Possibility of observing the direct thermal photon and lepton pair
from quark gluon plasma has been contrasted with those from hot hadronic matter
with and without medium effects for various mass variation scenarios. At SPS
energies, in-medium effects of different magnitude on the hadronic properties
for the Walecka model, Brown-Rho scaling and Nambu scaling scenarios are
conspicuously visible through the low invariant mass distribution of dilepton
and transverse momentum spectra of photon. However, at RHIC energies the
thermal photon (dilepton) spectra originating from Quark Gluon Plasma
overshines those from hadronic matter for large transverse momentum (invariant
mass) irrespective of the models used for evaluating the finite temperature
effects on the hadronic properties. It is thus expected that both at RHIC and
LHC energies the formation of Quark Gluon Plasma in the initial stages may
indeed turn out to be a realistic scenario.Comment: Text revised, 3 figures adde
Heat Capacity study of -FeSi single crystals
Heat Capacity of needle-like [length=5mm, diameter=1 mm] -FeSi
single crystal, grown by chemical vapor transport has been measured. Two
anomalies are found, a broad deviation centered around 160 K and a clear
deviation at a temperature of 255 K approximately. We have attempted to relate
these to the anomalies previously reported in the case of the resistivity data.
The Transient Thermoelectric Effect [TTE] results lead us to the inference that
the system under goes from single carrier system to at least two carrier system
at 220 K-our heat capacity results seem to provide further independent evidence
for this transition in this system.Comment: 8 pages, 5 figure
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