1,176 research outputs found
Observation of a temperature dependent electrical resistance minimum above the magnetic ordering temperature in GdPdSi
Results on electrical resistivity, magnetoresistance, magnetic Results on
electrical resistivity, magnetoresistance, magnetic susceptibility, heat
capacity and Gd Mossbauer measurements on a Gd-based intermetallic compound,
GdPdSi are reported. A finding of interest is that the resistivity
unexpectedly shows a well-defined minimum at about 45 K, well above the long
range magnetic ordering temperature (21 K), a feature which gets suppressed by
the application of a magnetic field. This observation in a Gd alloy presents an
interesting scenario. On the basis of our results, we propose electron
localization induced by s-f (or d-f) exchange interaction prior to long range
magnetic order as a mechanism for the electrical resistance minimum.Comment: 4 pages, 4 figure
Fluvial Sediment Aggradation and Incision in NW Sub-Himalaya
Abstract HKT-ISTP 2013
A
Relative importance of fluvial and glacial erosion in shaping the Chandra Valley, western Himalaya, India
Abstract HKT-ISTP 2013
B
Conversion of an Atomic Fermi Gas to a Long-Lived Molecular Bose Gas
We have converted an ultracold Fermi gas of Li atoms into an ultracold
gas of Li molecules by adiabatic passage through a Feshbach resonance.
Approximately molecules in the least-bound, ,
vibrational level of the X singlet state are produced with an
efficiency of 50%. The molecules remain confined in an optical trap for times
of up to 1 s before we dissociate them by a reverse adiabatic sweep.Comment: Accepted for publication in Phys. Rev. Letter
Neutron-induced background in the CONUS experiment
CONUS is a novel experiment aiming at detecting elastic neutrino nucleus
scattering in the fully coherent regime using high-purity Germanium (Ge)
detectors and a reactor as antineutrino () source. The detector setup
is installed at the commercial nuclear power plant in Brokdorf, Germany, at a
very small distance to the reactor core in order to guarantee a high flux of
more than 10/(scm). For the experiment, a good
understanding of neutron-induced background events is required, as the neutron
recoil signals can mimic the predicted neutrino interactions. Especially
neutron-induced events correlated with the thermal power generation are
troublesome for CONUS. On-site measurements revealed the presence of a thermal
power correlated, highly thermalized neutron field with a fluence rate of
(74530)cmd. These neutrons that are produced by nuclear
fission inside the reactor core, are reduced by a factor of 10 on
their way to the CONUS shield. With a high-purity Ge detector without shield
the -ray background was examined including highly thermal power
correlated N decay products as well as -lines from neutron
capture. Using the measured neutron spectrum as input, it was shown, with the
help of Monte Carlo simulations, that the thermal power correlated field is
successfully mitigated by the installed CONUS shield. The reactor-induced
background contribution in the region of interest is exceeded by the expected
signal by at least one order of magnitude assuming a realistic ionization
quenching factor of 0.2.Comment: 28 pages, 28 figure
A model for conservative chaos constructed from multi-component Bose-Einstein condensates with a trap in 2 dimensions
To show a mechanism leading to the breakdown of a particle picture for the
multi-component Bose-Einstein condensates(BECs) with a harmonic trap in high
dimensions, we investigate the corresponding 2- nonlinear Schr{\"o}dinger
equation (Gross-Pitaevskii equation) with use of a modified variational
principle. A molecule of two identical Gaussian wavepackets has two degrees of
freedom(DFs), the separation of center-of-masses and the wavepacket width.
Without the inter-component interaction(ICI) these DFs show independent regular
oscillations with the degenerate eigen-frequencies. The inclusion of ICI
strongly mixes these DFs, generating a fat mode that breaks a particle picture,
which however can be recovered by introducing a time-periodic ICI with zero
average. In case of the molecule of three wavepackets for a three-component
BEC, the increase of amplitude of ICI yields a transition from regular to
chaotic oscillations in the wavepacket breathing.Comment: 5 pages, 4 figure
Suppression of the ferromagnetic state in LaCoO3 films by rhombohedral distortion
Epitaxially strained LaCoO3 (LCO) thin films were grown with different film
thickness, t, on (001) oriented (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT)
substrates. After initial pseudomorphic growth the films start to relieve their
strain partly by the formation of periodic nano-twins with twin planes
predominantly along the direction. Nano-twinning occurs already at the
initial stage of growth, albeit in a more moderate way. Pseudomorphic grains,
on the other hand, still grow up to a thickness of at least several tenths of
nanometers. The twinning is attributed to the symmetry lowering of the
epitaxially strained pseudo-tetragonal structure towards the relaxed
rhombohedral structure of bulk LCO. However, the unit-cell volume of the
pseudo-tetragonal structure is found to be nearly constant over a very large
range of t. Only films with t > 130 nm show a significant relaxation of the
lattice parameters towards values comparable to those of bulk LCO.Comment: 31 pages, 10 figure
Effectively attractive Bose-Einstein condensates in a rotating toroidal trap
We examine an effectively attractive quasi-one-dimensional Bose-Einstein
condensate of atoms confined in a rotating toroidal trap, as the magnitude of
the coupling constant and the rotational frequency are varied. Using both a
variational mean-field approach, as well as a diagonalization technique, we
identify the phase diagram between a uniform and a localized state and we
describe the system in the two phases.Comment: 4 pages, 4 ps figures, RevTe
Gap solitons in superfluid boson-fermion mixtures
Using coupled equations for the bosonic and fermionic order parameters, we
construct families of gap solitons (GSs) in a nearly one-dimensional Bose-Fermi
mixture trapped in a periodic optical-lattice (OL) potential, the boson and
fermion components being in the states of the BEC and BCS superfluid,
respectively. Fundamental GSs are compact states trapped, essentially, in a
single cell of the lattice. Full families of such solutions are constructed in
the first two bandgaps of the OL-induced spectrum, by means of variational and
numerical methods, which are found to be in good agreement. The families
include both intra-gap and inter-gap solitons, with the chemical potentials of
the boson and fermion components falling in the same or different bandgaps,
respectively.Nonfundamental states, extended over several lattice cells, are
constructed too. The GSs are stable against strong perturbations.Comment: 9 pages, 14 figure
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