96 research outputs found
Ground state of two-component degenerate fermionic gases
We analyze the ground state of the two--component gas of trapped ultracold
fermionic atoms. We neglect the forces between atoms in the same hyperfine
state (the same component). For the case when the forces between
distinguishable atoms (i.e., atoms in different hyperfine states) are repulsive
(positive mutual scattering length), we find the existence of critical
interaction strength above which one atomic fraction expels the other from the
center of the trap. When atoms from different components attract each other
(negative mutual scattering length) the ground state of the system dramatically
changes its structure for strong enough attraction -- the Cooper pairs built of
atoms in different hyperfine states appear.Comment: 10 pages, 14 figure
Shock waves in ultracold Fermi (Tonks) gases
It is shown that a broad density perturbation in a Fermi (Tonks) cloud takes
a shock wave form in the course of time evolution. A very accurate analytical
description of shock formation is provided. A simple experimental setup for the
observation of shocks is discussed.Comment: approx. 4 pages&figures, minor corrections^2, to be published as a
Letter in Journal of Physics
On the stability of Bose-Fermi mixtures
We consider the stability of a mixture of degenerate Bose and Fermi gases.
Even though the bosons effectively repel each other the mixture can still
collapse provided the Bose and Fermi gases attract each other strongly enough.
For a given number of atoms and the strengths of the interactions between them
we find the geometry of a maximally compact trap that supports the stable
mixture. We compare a simple analytical estimation for the critical axial
frequency of the trap with results based on the numerical solution of
hydrodynamic equations for Bose-Fermi mixture.Comment: 4 pages, 3 figure
Splitting of doubly quantized vortices in dilute Bose-Einstein condensates
We investigate the dynamics of doubly charged vortices generated in dilute
Bose-Einstein condensates by using the topological phase imprinting technique.
We find splitting times of such vortices and show that thermal atoms are
responsible for their decay.Comment: 1 page, 1 figur
Low-energy three-body dynamics in binary quantum gases
The universal three-body dynamics in ultra-cold binary Fermi and Fermi-Bose
mixtures is studied. Two identical fermions of the mass and a particle of
the mass with the zero-range two-body interaction in the states of the
total angular momentum L=1 are considered. Using the boundary condition model
for the s-wave interaction of different particles, both eigenvalue and
scattering problems are treated by solving hyper-radial equations, whose terms
are derived analytically. The dependencies of the three-body binding energies
on the mass ratio for the positive two-body scattering length are
calculated; it is shown that the ground and excited states arise at and ,
respectively. For m/m_1 \alt \lambda_1 and m/m_1 \alt \lambda_2, the
relevant bound states turn to narrow resonances, whose positions and widths are
calculated. The 2 + 1 elastic scattering and the three-body recombination near
the three-body threshold are studied and it is shown that a two-hump structure
in the mass-ratio dependencies of the cross sections is connected with arising
of the bound states.Comment: 16 page
Phase separation of a repulsive two-component Fermi gas at the two- to three-dimensional crossover
We present a theoretical analysis of phase separations between two
repulsively interacting components in an ultracold fermionic gas, occurring at
the dimensional crossover in a harmonic trap with varying aspect ratios. A
tailored kinetic energy functional is derived and combined with a
density-potential functional approach to develop a framework that is
benchmarked with the orbital-based method. We investigate the changes in the
density profile of the phase-separated gas under different interaction
strengths and geometries. The analysis reveals the existence of small,
partially polarized domains in certain parameter regimes, which is similar to
the purely two-dimensional limit. However, the density profile is further
enriched by a shell structure found in anisotropic traps. We also track the
transitions that can be driven by either a change in interaction strength or
trap geometry. The developed framework is noted to have applications for other
systems with repulsive interactions that combine continuous and discrete
degrees of freedom.Comment: 14 pages, 4 figure
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