1,037 research outputs found
A Glimpse of Michigan and Her National Forest
Very interesting it would be to mention the word Michigan to an audience of people more or less familiar with the state and then have flashed on a screen in rapid succession the pictures of what would appear in the minds of each individual. Automobiles, mostly Fords, of course, would no doubt lead the list. Following in their order would then come the Great Lakes, large cities and industries, agriculture, educational institutions, fruit farms, iron and copper mines, good roads, miles of shore line, summer resorts, fish and game and so on down the list of things that all go to display and define a most wonderful State. A few, no doubt, would think of vanishing forests, thousands of idle acres, forest fires and the work being done by the Government and State along Forestry lines, but how much in the minority would be these minds dwelling entirely on futures. It is not unreasonable, therefore, that Forestry is moving slowly in Michigan, nor can it be expected to move faster until forest fires, the scarcity of lumber products, and idle acres become at least as important as Fords in the minds of the majority
Mixing-Demixing transition in 1D boson-fermion mixture at low fermion densities
We numerically investigated the mixing-demixing transition of the
boson-fermion mixture on a 1D lattice at an incommensurate filling with the
fermion density being kept below the boson density. The phase diagram we
obtained suggested that the decrease of the number of the fermions drove the
system into the demixing phase
Bose Einstein Condensate in a Box
Bose-Einstein condensates have been produced in an optical box trap. This
novel optical trap type has strong confinement in two directions comparable to
that which is possible in an optical lattice, yet produces individual
condensates rather than the thousands typical of a lattice. The box trap is
integrated with single atom detection capability, paving the way for studies of
quantum atom statistics.Comment: 4 pages, 5 figure
Feshbach resonances in the 6Li-40K Fermi-Fermi mixture: Elastic versus inelastic interactions
We present a detailed theoretical and experimental study of Feshbach
resonances in the 6Li-40K mixture. Particular attention is given to the
inelastic scattering properties, which have not been considered before. As an
important example, we thoroughly investigate both elastic and inelastic
scattering properties of a resonance that occurs near 155 G. Our theoretical
predictions based on a coupled channels calculation are found in excellent
agreement with the experimental results. We also present theoretical results on
the molecular state that underlies the 155G resonance, in particular concerning
its lifetime against spontaneous dissociation. We then present a survey of
resonances in the system, fully characterizing the corresponding elastic and
inelastic scattering properties. This provides the essential information to
identify optimum resonances for applications relying on interaction control in
this Fermi-Fermi mixture.Comment: Submitted to EPJD, EuroQUAM special issues "Cold Quantum Matter -
Achievements and Prospects", v2 with updated calibration of magnetic field
(+4mG correction) and updated figures 4 and
Direct Observation of Sub-Poissonian Number Statistics in a Degenerate Bose Gas
We report the direct observation of sub-Poissonian number fluctuation for a
degenerate Bose gas confined in an optical trap. Reduction of number
fluctuations below the Poissonian limit is observed for average numbers that
range from 300 to 60 atoms.Comment: 5 pages, 4 figure
Fermi-Bose quantum degenerate ^40 K - ^87 Rb mixture with attractive interaction
We report on the achievement of simultaneous quantum degeneracy in a mixed
gas of fermionic ^40 K and bosonic ^87 Rb. Potassium is cooled to 0.3 times the
Fermi temperature by means of an efficient thermalization with evaporatively
cooled rubidium. Direct measurement of the collisional cross-section confirms a
large interspecies attraction. This interaction is shown to affect the
expansion of the Bose-Einstein condensate released form the magnetic trap,
where it is immersed in the Fermi sea.Comment: 5 pages, 4 figures, replaced one figure plus some change
Reentrant superconductivity in superconductor/ferromagnetic-alloy bilayers
We studied the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like state
establishing due to the proximity effect in superconducting Nb/Cu41Ni59
bilayers. Using a special wedge-type deposition technique, series of 20-35
samples could be fabricated by magnetron sputtering during one run. The layer
thickness of only a few nanometers, the composition of the alloy, and the
quality of interfaces were controlled by Rutherford backscattering
spectrometry, high resolution transmission electron microscopy, and Auger
spectroscopy. The magnetic properties of the ferromagnetic alloy layer were
characterized with superconducting quantum interference device (SQUID)
magnetometry. These studies yield precise information about the thickness, and
demonstrate the homogeneity of the alloy composition and magnetic properties
along the sample series. The dependencies of the critical temperature on the Nb
and Cu41Ni59 layer thickness, Tc(dS) and Tc(dF), were investigated for constant
thickness dF of the magnetic alloy layer and dS of the superconducting layer,
respectively. All types of non-monotonic behaviors of Tc versus dF predicted by
the theory could be realized experimentally: from reentrant superconducting
behavior with a broad extinction region to a slight suppression of
superconductivity with a shallow minimum. Even a double extinction of
superconductivity was observed, giving evidence for the multiple reentrant
behavior predicted by theory. All critical temperature curves were fitted with
suitable sets of parameters. Then, Tc(dF) diagrams of a hypothetical F/S/F
spin-switch core structure were calculated using these parameters. Finally,
superconducting spin-switch fabrication issues are discussed in detail in view
of the achieved results.Comment: 34 pages, 9 figure
Shift of the molecular bound state threshold in dense ultracold Fermi gases with Feshbach resonance
We consider a dense ultracold Fermi gas in the presence of a Feshbach
resonance. We investigate how the treshold for bound state formation, which is
just at the Feshbach resonance for a dilute gas, is modified due to the
presence of the Fermi sea. We make use of a preceding framework of handling
this many-body problem. We restrict ourselves to the simple case where the
chemical potential is negative, which allows us to cover in particular
the classical limit where the effect is seen to disappear. We show that, within
a simple approach where basically only the effect of Pauli exclusion is
included, the Fermi sea produces a large shift of the threshold, which is of
order of the width of the Feshbach resonance. This is in agreement with very
recent experimental findings.Comment: one reference adde
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