4,358 research outputs found
Phase Separation in Bose-Fermi-Fermi Mixtures as a Probe of Fermi Superfluidity
We study the phase diagram of a mixture of Bose-Einstein condensate and a
two-component Fermi gas. In particular, we identify the regime where the
homogeneous system becomes unstable against phase separation. We show that,
under proper conditions, the phase separation phenomenon can be exploited as a
robust probe of Fermi superfluid
Possible magnetic-field-induced voltage and thermopower in diluted magnetic semiconductors
In diluted magnetic semiconductors, the carrier concentration and the
magnetization of local moments are strongly coupled, since the magnetic
interaction is mediated by the carriers. It is predicted that this coupling
leads to an electric polarization due to an applied magnetic-field gradient and
to the appearance of a magnetic-field-dependent voltage. An expression for this
voltage is derived within Landau theory and its magnitude is estimated for
(Ga,Mn)As. Furthermore, a large contribution to the thermopower based on the
same mechanism is predicted. The role of fluctuations is also discussed. These
predictions hold both if the magnetization is uniform and if it shows
stripe-like modulations, which are possible at lower temperatures.Comment: 6 pages revtex, 5 figure
Single Impurity In Ultracold Fermi Superfluids
The role of impurities as experimental probes in the detection of quantum
material properties is well appreciated. Here we study the effect of a single
classical magnetic impurity in trapped ultracold Fermi superfluids. Depending
on its shape and strength, a magnetic impurity can induce single or multiple
mid-gap bound states in a superfluid Fermi gas. The multiple mid-gap states
could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) phase within the superfluid. As an analog of the Scanning Tunneling
Microscope, we propose a modified RF spectroscopic method to measure the local
density of states which can be employed to detect these states and other
quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de
Gennes calculations is that a magnetic impurity can controllably induce an FFLO
state at currently accessible experimental parameters.Comment: 5 pages, 3 figures; added calculations for 3
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The occipital lateral plate mesoderm is a novel source for vertebrate neck musculature
In vertebrates, body musculature originates from somites, whereas head muscles originate from the cranial mesoderm. Neck muscles are located in the transition between these regions. We show that the chick occipital lateral plate mesoderm has myogenic capacity and gives rise to large muscles located in the neck and thorax. We present molecular and genetic evidence to show that these muscles not only have a unique origin, but additionally display a distinct temporal development, forming later than any other muscle group described to date. We further report that these muscles, found in the body of the animal, develop
like head musculature rather than deploying the programme used by the trunk muscles. Using mouse genetics we reveal that these muscles are formed in trunk muscle mutants but are absent in head muscle mutants. In concordance with this conclusion, their connective tissue is neural crest in origin. Finally, we provide evidence that the mechanism by which these neck muscles develop is conserved in vertebrates
Bogoliubov-de Gennes study of trapped spin-imbalanced unitary Fermi gases
It is quite common that several different phases exist simultaneously in a
system of trapped quantum gases of ultra-cold atoms. One such example is the
strongly-interacting Fermi gas with two imbalanced spin species, which has
received a great amount of attention due to the possible presence of exotic
superfluid phases. By employing novel numerical techniques and algorithms, we
self-consistently solve the Bogoliubov de-Gennes equations, which describe
Fermi superfluids in the mean-field framework. From this study, we investigate
the novel phases of spin-imbalanced Fermi gases and examine the validity of the
local density approximation (LDA), which is often invoked in the extraction of
bulk properties from experimental measurements within trapped systems. We show
how the validity of the LDA is affected by the trapping geometry, number of
atoms and spin imbalance.Comment: 15 pages, 5 figures, to be published in New J. Phys. (focus issue on
"Strongly Correlated Quantum Fluids: From Ultracold Quantum Gases to QCD
Plasmas"
Phase separation of Bose-Einstein condensates
The zero-temperature system of two dilute overlapping Bose-Einstein
condensates is unstable against long wavelength excitations if the interaction
strength between the distinguishable bosons exceeds the geometric mean of the
like-boson interaction strengths. If the condensates attract each other, the
instability is similar to the instability of the negative scattering length
condensates. If the condensates repel, they separate spatially into condensates
of equal pressure. We estimate the boundary size, surface tension and energy of
the phase separated condensate system and we discuss the implications for
double condensates in atomic traps.Comment: 11 pages, 1 figur
Comparing placentas from normal and abnormal pregnancies
This report describes work carried out at a Mathematics-in-Medicine Study Group. It is believed that placenta shape villous network characteristics are strongly linked to the placenta’s efficiency, and hence to pregnancy outcome. We were asked to consider mathematical ways to describe the shape and other characteristics of a placenta, as well as forming mathematical models for placenta development. In this report we propose a number of possible measure of placental shape, form, and efficiency, which can be computed from images already obtained. We also consider various models for the early development of placentas and the growth of the villous tree
Eliminating the mean-field shift in multicomponent Bose-Einstein condensates
We demonstrate that the nonlinear mean-field shift in a multi-component
Bose-Einstein condensate may be eliminated by controlling the two-body
interaction coefficients. This modification is achieved by, e.g., suitably
engineering the environment of the condensate. We consider as an example the
case of a two-component condensate in a tightly confining atom waveguide.
Modification of the atom-atom interactions is then achieved by varying
independently the transverse wave function of the two components. Eliminating
the density dependent phase shift in a high-density atomic beam has important
applications in atom interferometry and precision measurement
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