4,684 research outputs found
Comment on ``Phase and Phase Diffusion of a Split Bose-Einstein Condensate''
Recently Javanainen and Wilkens [Phys. Rev. Lett. 78, 4675 (1997)] have
analysed an experiment in which an interacting Bose condensate, after being
allowed to form in a single potential well, is "cut" by splitting the well
adiabatically with a very high potential barrier, and estimate the rate at
which, following the cut, the two halves of the condensate lose the "memory" of
their relative phase. We argue that, by neglecting the effect of interactions
in the initial state before the separation, they have overestimated the rate of
phase randomization by a numerical factor which grows with the interaction
strength and with the slowness of the separation process.Comment: 2 pages, no figures, to appear in Phys. Rev. Let
Zero Temperature Thermodynamics of Asymmetric Fermi Gases at Unitarity
The equation of state of a dilute two-component asymmetric Fermi gas at
unitarity is subject to strong constraints, which affect the spatial density
profiles in atomic traps. These constraints require the existence of at least
one non-trivial partially polarized (asymmetric) phase. We determine the
relation between the structure of the spatial density profiles and the T=0
equation of state, based on the most accurate theoretical predictions
available. We also show how the equation of state can be determined from
experimental observations.Comment: 10 pages and 7 figures. (Minor changes to correspond with published
version.
On Koopman-von Neumann Waves II
In this paper we continue the study, started in [1], of the operatorial
formulation of classical mechanics given by Koopman and von Neumann (KvN) in
the Thirties. In particular we show that the introduction of the KvN Hilbert
space of complex and square integrable "wave functions" requires an enlargement
of the set of the observables of ordinary classical mechanics. The possible
role and the meaning of these extra observables is briefly indicated in this
work. We also analyze the similarities and differences between non selective
measurements and two-slit experiments in classical and quantum mechanics.Comment: 18+1 pages, 1 figure, misprints fixe
Stable Sarma State in Two-band Fermi Systems
We investigate fermionic superconductivity with mismatched Fermi surfaces in
a general two-band system. The exchange interaction between the two bands
changes significantly the stability structure of the pairing states. The Sarma
state with two gapless Fermi surfaces which is always unstable in single-band
systems, can be the stable ground state in two-band systems. To realize a
visible mismatch window for the stable Sarma state, two conditions should be
satisfied: a nonzero inter-band exchange interaction and a large asymmetry
between the two bands.Comment: V3: Version published in Physical Review
Phase diagram of a polarized Fermi gas across a Feshbach resonance in a potential trap
We map out the detailed phase diagram of a trapped ultracold Fermi gas with
population imbalance across a wide Feshbach resonance. We show that under the
local density approximation, the properties of the atoms in any (anisotropic)
harmonic traps are universally characterized by three dimensionless parameters:
the normalized temperature, the dimensionless interaction strength, and the
population imbalance. We then discuss the possible quantum phases in the trap,
and quantitatively characterize their phase boundaries in various typical
parameter regions.Comment: 9 pages, 4 figure
Profiles of near-resonant population-imbalanced trapped Fermi gases
We investigate the density profiles of a partially polarized trapped Fermi
gas in the BCS-BEC crossover region using mean field theory within the local
density approximation. Within this approximation the gas is phase separated
into concentric shells. We describe how the structure of these shells depends
upon the polarization and the interaction strength. A Comparison with
experiments yields insight into the possibility of a polarized superfluid
phase.Comment: 4 pages, 5 Figures, Published versio
Cooper pairing and BCS-BEC evolution in mixed-dimensional Fermi gases
Similar to what has recently been achieved with Bose-Bose mixtures [Lamporesi
et al., Phys. Rev. Lett. 104, 153202 (2010)], mixed-dimensional Fermi-Fermi
mixtures can be created by applying a species-selective one-dimensional optical
lattice to a two-species Fermi gas (),
such a way that only one of the species feel the lattice potential and is
confined to a quasi-two-dimensional geometry, while having negligible effect on
the other, that is leaving it three dimensional. We investigate the ground
state phase diagram of superfluidity for such mixtures in the BCS-BEC
evolution, and find normal, gapped superfluid, gapless superfluid, and phase
separated regions. In particular, we find a stable gapless superfluid phase
where the unpaired and fermions coexist with the paired
(or superfluid) ones in different momentum space regions. This phase is in some
ways similar to the Sarma state found in mixtures with unequal densities, but
in our case, the gapless superfluid phase is unpolarized and most importantly
it is stable against phase separation.Comment: 8 pages with 4 figure
Pairing in Asymmetrical Fermi Systems with Intra- and Inter-Species Correlations
We consider inter- and intra-species pairing interactions in an asymmetrical
Fermi system. Using equation of motion method, we obtain coupled mean-field
equations for superfluid gap functions and population densities. We construct a
phase diagram across BCS-BEC regimes. Due to intra-species correlations, the
BCS singlet superfluid state can sustain finite polarizations, . For larger
, we find phase separations in BCS and BEC regimes. A superfluid phase
exists for all deep in BEC regime. Our results may apply to pairing in
ultracold fermions, nuclear and quark matter physics.Comment: Contents revised. Added reference
Quantitative Probe of Pairing Correlations in a Cold Fermionic Atom Gas
A quantitative measure of the pairing correlations present in a cold gas of
fermionic atoms can be obtained by studying the dependence of RF spectra on
hyperfine state populations. This proposal follows from a sum rule that relates
the total interaction energy of the gas to RF spectrum line positions. We argue
that this indicator of pairing correlations provides information comparable to
that available from the spin-susceptibility and NMR measurements common in
condensed-matter systems.Comment: 5 pages, 1 figur
Stability of the Breached Pair State for a Two-species Fermionic System in the Presence of Feshbach Resonance
We investigate the phenomenon of fermionic pairing with mismatched Fermi
surfaces in a two-species system in the presence of Feshbach resonance, where
the resonantly-paired fermions combine to form bosonic molecules. We observe
that the Feshbach parameters control the critical temperature of the gapped BCS
superfluid state, and also determine the range over which a gapless breached
pair state may exist. Demanding the positivity of the superfluid density, it is
shown that although a breached pair state with two Fermi surfaces is always
unstable, its single Fermi-surface counterpart can be stable if the chemical
potentials of the two pairing species have opposite signs. This condition is
satisfied only over a narrow region in the BEC side, characterized by an upper
and a lower limit for the magnetic field. We estimate these limits for a
mixture of two hyperfine states of Li using recent experimental data.Comment: 14 pages,5 figure
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