5,956 research outputs found
Topological Weyl Superconductor to Diffusive Thermal Hall Metal Crossover in the B-Phase of UPt
The recent phase sensitive measurements in the superconducting -phase of
UPt provide strong evidence for the triplet, chiral
pairing symmetries, which endow the Cooper pairs with orbital angular momentum
projections along the -axis. In the absence of disorder such
pairing can support both line and point nodes, and both types of nodal
quasiparticles exhibit nontrivial topology in the momentum space. The point
nodes, located at the intersections of the closed Fermi surfaces with the
-axis, act as the double monopoles and the antimonopoles of the Berry
curvature, and generalize the notion of Weyl quasiparticles. Consequently, the
phase should support an anomalous thermal Hall effect, the polar Kerr
effect, in addition to the protected Fermi arcs on the (1,0,0) and the (0,1,0)
surfaces. The line node at the Fermi surface equator acts as a vortex loop in
the momentum space and gives rise to the zero energy, dispersionless Andreev
bound states on the (0,0,1) surface. At the transition from the -phase to
the -phase, the time reversal symmetry is restored, and only the line node
survives inside the -phase. As both line and double-Weyl point nodes possess
linearly vanishing density of states, we show that weak disorder acts as a
marginally relevant perturbation. Consequently, an infinitesimal amount of
disorder destroys the ballistic quasiparticle pole, while giving rise to a
diffusive phase with a finite density of states at the zero energy. The
resulting diffusive phase exhibits -linear specific heat, and an anomalous
thermal Hall effect. We predict that the low temperature thermodynamic and
transport properties display a crossover between a ballistic thermal Hall
semimetal and a diffusive thermal Hall metal.Comment: 8 pages, 1 figure; replaced by the version accepted by Phys. Rev.
Formation of caustics in Dirac-Born-Infeld type scalar field systems
We investigate the formation of caustics in Dirac-Born-Infeld type scalar
field systems for generic classes of potentials, viz., massive rolling scalar
with potential, and inverse
power-law potentials with . We find that in the case
of\texttt{} exponentially decreasing rolling massive scalar field potential,
there are multi-valued regions and regions of likely to be caustics in the
field configuration. However there are no caustics in the case of exponentially
increasing potential. We show that the formation of caustics is inevitable for
the inverse power-law potentials under consideration in Minkowski space time
whereas caustics do not form in this case in the FRW universe.Comment: 16 pages, 14 figures, major revision, conclusions strengthen, to
appear in PR
Clean-up of Contaminated Indoor Air Using Photocatalytic Technology
A number of Sick Building Syndrome
studies have concluded that microorganisms,
endotoxins and VOCs in indoor air are involved in
the development and/or aggravation of allergies and
illnesses in buildings. The phototcatalytic indoor air
disinfection and detoxification technology provides
one of the most viable solutions to the growing need
to remediate and purify contaminated indoor air.
The experiments were conducted in a stainless steel
environmental chamber to quantitatively measure the
photocatalytic VOC destruction using Acetone as a
representative VOC. While monitoring the VOC
destruction, carbon dioxide (C02) levels were also
measured. By performing a mass balance between
the VOC destruction and C02 production, the
photocatalytic technology was found to be
completely effective. Dark control experiments were
performed for each condition to confirm the validity
of each experiment. The photocatalytic technology
tested in these experiments was demonstrated to
completely oxidize acetone at normal indoor air
atmospheric conditions
Global oscillation analysis of solar neutrino data with helioseismically constrained fluxes
A seismic model for the Sun calculated using the accurate helioseismic data
predicts a lower neutrino flux as compared to the standard solar
model (SSM). However, there persists a discrepancy between the predicted and
measured neutrino fluxes and it seems necessary to invoke neutrino oscillations
to explain the measurements. In this work, we have performed a global, unified
oscillation analysis of the latest solar neutrino data (including the results
of SNO charged current rate) using the seismic model fluxes as theoretical
predictions. We determine the best-fit values of the neutrino oscillation
parameters and the for both
and cases and present the allowed parameter
regions in the plane for transition. The results are compared with those obtained using the
latest SSM by Bahcall and his collaborators.Comment: Version to appear in Phys. Rev.
Laser phase modulation approaches towards ensemble quantum computing
Selective control of decoherence is demonstrated for a multilevel system by
generalizing the instantaneous phase of any chirped pulse as individual terms
of a Taylor series expansion. In the case of a simple two-level system, all odd
terms in the series lead to population inversion while the even terms lead to
self-induced transparency. These results also hold for multiphoton transitions
that do not have any lower-order photon resonance or any intermediate virtual
state dynamics within the laser pulse-width. Such results form the basis of a
robustly implementable CNOT gate.Comment: 10 pages, 4 figures, PRL (accepted
Rapid Determination of Iron in Water by Modified Thiocyanate Method
A rapid spectrophotometric method for determination of iron in water by oxidising ferrous iron with ceric ammonium sulphate at roomtemperature followed by formation of ferric thiocyanate colour complexwith potassium thiocyanate has been described. The method is simple and rapid as compared to other standard methods used in water analysis and iron content of water upto 5 ppm can be determined by this method with a maximum error of 2.8 per cen
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