19,830 research outputs found
Improved transfer efficiency with pulsed atom transfer between two magneto-optical traps
In our double magneto-optical trap (MOT) setup containing a vapor chamber MOT
(VC-MOT) and an ultra high vacuum MOT (UHV-MOT) for Rb atoms, we find
that transfer of atoms from VC-MOT to UHV-MOT can be enhanced by employing a
pulsed VC-MOT loading followed by a pulsed push beam, as compared to that
obtained by focusing a continuous wave (CW) push beam on a continuously loaded
VC-MOT. By choosing appropriately the VC-MOT duration and push beam duration,
the number of atoms in UHV-MOT was 3-times the number obtained with a
continuous VC-MOT and a CW push beam of optimized power. The processes
affecting the pulsed transfer have been studied.Comment: 10 pages, 4 figure
Quantum well structure of a double perovskite superlattice and formation of a spin-polarized two-dimensional electron gas
Layered oxide heterostructures are the new routes to tailor desired
electronic and magnetic phases emerging from competing interactions involving
strong correlation, orbital hopping, tunnelling and lattice coupling phenomena.
Here, we propose a half-metal/insulator superlattice that intrinsically forms
spin-polarized two-dimensional electron gas (2DEG) following a mechanism very
different from the widely reported 2DEG at the single perovskite polar
interfaces. From DFT study on SrFeMoO/LaCoMnO (001)
superlattice, we find that a periodic quantum well is created along [001] which
breaks the three-fold degeneracy to separate the doubly degenerate
and states from the planar state. In the spin-down channel, the
dual effect of quantum confinement and strong correlation localizes the
degenerate states, whereas the dispersive state forms the 2DEG which is
robust against perturbations to the superlattice symmetry. The spin-up channel
retains the bulk insulating. Both spin polarization and orbital polarization
make the superlattice ideal for spintronic and orbitronic applications. The
suggested 2DEG mechanism widens the scope of fabricating next generation of
oxide heterostructures.Comment: 10 pages, 12 figure
Resonant magneto-optic rotation for magnetometry using autonomous frequency stabilization
The operation of a high sensitive atomic magnetometer using resonant
elliptically polarized light is demonstrated. The experimental geometry allows
autonomous frequency stabilization of the laser, thereby offers compact
operation of the overall device. The magnetometry is based on measurement of
the zero magnetic field resonance in degenerate two level system using
polarimetric detection and has a preliminary sensitivity of <10 pT/Hz1/2 @ 1
Hz.Comment: 4 page
Probing of Structural Phase Transitions in Barium Titanate Modified Sodium Niobate using Raman Scattering
Raman Spectroscopic measurements are carried out to investigate the
structural phase transitions as a function of composition in modified sodium
niobate [(1-x) NaNbO3-xBaTiO3:NNBTx] for x=0.0 to 0.15 at room temperature. The
characteristic antiferroelectric modes at around 93.4 and 123.6cm-1alongwith a
mode at 155.5 cm-1were found to disappear across the structural phase
transition from antiferroelectric orthorhombic phase (Pbcm) to ferroelectric
orthorhombic phase (Pmc21) phase for x>0.02. The redistribution of intensities
and positions of the Raman lines in bending (150-350 cm-1) and stretching modes
(>550cm-1) on increasing the concentration x>0.05 also confirms the occurrence
of another phase transition from ferroelectric orthorhombic phase (Pmc21) to
another ferroelectric orthorhombic phase (Amm2) phase across x~0.10.The phase
transitions as observed from Raman measurements are consistent with previous
x-ray diffraction study.Comment: 16 Pages, 4 Figure
Temperature and phase-space density of cold atom cloud in a quadrupole magnetic trap
We present studies on the modifications in temperature, number density and
phase-space density when a laser cooled atom cloud from the optical molasses is
trapped in a quadrupole magnetic trap. Theoretically it is shown that for a
given temperature and size of the cloud from the molasses, the phase-space
density in the magnetic trap first increases with magnetic field gradient and
then decreases with it, after attaining a maximum value at an optimum value of
magnetic field gradient. The experimentally measured variation in phase-space
density in the magnetic trap with the magnetic field gradient has shown the
similar trend. However, the experimentally measured values of number density
and phase-space density are much lower than their theoretically predicted
values. This is attributed to the higher experimentally observed temperature in
the magnetic trap than the theoretically predicted temperature. Nevertheless,
these studies can be useful to set a higher phase-space density in the trap by
setting the optimum value of field gradient of the quadrupole magnetic trap.Comment: 9 pages, 7 figure
Electromagnetically Induced Transparency in -systems of atom in magnetic field
The electromagnetically induced transparency (EIT) observations in two
-systems of atom, and
, have been investigated in detail and the results are
found consistent with our proposed theoretical models. The second
-system provides EIT signal with higher magnitude than the first
system, both in absence and in presence of an applied magnetic field. The
observed steeper slope of the EIT signal in presence of the magnetic field can
enable one to achieve tight frequency locking of lasers using these EIT
signals.Comment: 9 Figures and 8 page
On the rupture of DNA molecule
Using Langevin Dynamic simulations, we study effects of the shear force on
the rupture of a double stranded DNA molecule. The model studied here contains
two single diblock copolymers interacting with each other. The elastic
constants of individual segments of the diblock copolymer are considered to be
different. We showed that the magnitude of the rupture force depends on whether
the force is applied at ends or ends. Distributions of
extension in hydrogen bonds and covalent bonds along the chain show the
striking differences. Motivated by recent experiments, we have also calculated
the variation of rupture force for different chain lengths. Results obtained
from simulations have been validated with the analytical calculation based on
the ladder model of DNA.Comment: 7 pages and 4 figure
Suppression of Antiferroelectric State in NaNbO3 at High Pressure from In Situ Neutron Diffraction
We report direct experimental evidence of antiferroelectric to paraelectric
phase transition under pressure in NaNbO3 using neutron diffraction at room
temperature. The paraelectric phase is found to stabilize above 8 GPa and its
crystal structure has been determined in orthorhombic symmetry with space group
Pbnm. The variation of the structural parameters of the both orthorhombic
phases as a function of pressure was determined. We have not found evidence for
structural phase transition around 2 GPa as previously suggested in the
literature based on Raman scattering experiments, however, significant change
in Nb-O-Nb bond angles are found around this pressure. The response of the
lattice parameters to pressure is strongly anisotropic with a largest
contraction along . The structural phase transition around ~ 8 GPa is
followed by an anomalous increase in the orthorhombic strain and tilt angle
associated with the R point (q= 1/2 1/2 1/2). Ab-initio calculation of the
enthalpy in the various phases of NaNbO3 is able to predict the phase
transition pressure well.Comment: 14 Pages, 6 Figures, 1 tabl
Rotation Adaptive Visual Object Tracking with Motion Consistency
Visual Object tracking research has undergone significant improvement in the
past few years. The emergence of tracking by detection approach in tracking
paradigm has been quite successful in many ways. Recently, deep convolutional
neural networks have been extensively used in most successful trackers. Yet,
the standard approach has been based on correlation or feature selection with
minimal consideration given to motion consistency. Thus, there is still a need
to capture various physical constraints through motion consistency which will
improve accuracy, robustness and more importantly rotation adaptiveness.
Therefore, one of the major aspects of this paper is to investigate the outcome
of rotation adaptiveness in visual object tracking. Among other key
contributions, the paper also includes various consistencies that turn out to
be extremely effective in numerous challenging sequences than the current
state-of-the-art.Comment: Accepted conference paper WACV 201
Low field magnetoelectric effect in Fe substituted Co4Nb2O9
Co4Nb2O9 (CNO) having {\alpha}-Al2O3 crystal structure with Co chains along
c-direction shows gigantic magnetoelelctric coupling below antiferromagnetic
ordering temperature of 27 K but above a spin flop field of 1.6 T. We have
investigated structural, magnetic and magnetoelectric properties of Fe
substituted (10% and 20%) samples and compared with the parent one. In fact
magnetic and specific heat measurements have revealed an additional magnetic
transition below 10 K and presence of short range magnetic ordering above ~ 50
K in parent as well as in Fe substituted samples. Linear magnetoelelctric and
ferroelectric behaviours are evidenced in the Fe substituted samples where an
electric field of 5 kV/m is sufficient to align the dipoles and the
magnetoelelctric coupling is ensured for magnetic fields as low as 0.25 T, far
below the spin flop field.Comment: 13 page
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