15 research outputs found
Control of Ultracold Collisions with Frequency-Chirped Light
We report on ultracold atomic collision experiments utilizing frequency-chirped laser light. A rapid
chirp below the atomic resonance results in adiabatic excitation to an attractive molecular potential over a
wide range of internuclear separation. This leads to a transient inelastic collision rate which is large
compared to that obtained with fixed-frequency excitation. The combination of high efficiency and
temporal control demonstrates the benefit of applying the techniques of coherent control to the ultracold
domain
Dynamics of trapped two-component Fermi gas: temperature dependence of the transition from collisionless to collisional regime
We develop a numerical method to study the dynamics of a two-component atomic
Fermi gas trapped inside a harmonic potential at temperature T well below the
Fermi temperature Tf. We examine the transition from the collisionless to the
collisional regime down to T=0.2 Tf and find good qualitative agreement with
the experiments of B. DeMarco and D.S. Jin [Phys. Rev. Lett. vol. 88, 040405
(2002)]. We demonstrate a twofold role of temperature on the collision rate and
on the efficiency of collisions. In particular we observe an hitherto
unreported effect, namely that the transition to hydrodynamic behavior is
shifted towards lower collision rates as temperature decreases.Comment: 4 pages, 3 figure
Temperature dependence of density profiles for a cloud of non-interacting fermions moving inside a harmonic trap in one dimension
We extend to finite temperature a Green's function method that was previously
proposed to evaluate ground-state properties of mesoscopic clouds of
non-interacting fermions moving under harmonic confinement in one dimension. By
calculations of the particle and kinetic energy density profiles we illustrate
the role of thermal excitations in smoothing out the quantum shell structure of
the cloud and in spreading the particle spill-out from quantum tunnel at the
edges. We also discuss the approach of the exact density profiles to the
predictions of a semiclassical model often used in the theory of confined
atomic gases at finite temperature.Comment: 7 pages, 4 figure
Collisionless and hydrodynamic excitations of trapped boson-fermion mixtures
Within a scaling ansatz formalism plus Thomas-Fermi approximation, we
investigate the collective excitations of a harmonically trapped boson-fermion
mixture in the collisionless and hydrodynamic limit at low temperature. Both
the monopole and quadrupole modes are considered in the presence of spherical
as well as cylindrically symmetric traps. In the spherical traps, the frequency
of monopole mode coincides in the collisionless and hydrodynamic regime,
suggesting that it might be undamped in all collisional regimes. In contrast,
for the quadrupole mode, the frequency differs largely in these two limits. In
particular, we find that in the hydrodynamic regime the quadrupole oscillations
with equal bosonic and fermionic amplitudes generate an exact eigenstate of the
system, regardless of the boson-fermion interaction. This resembles the Kohn
mode for the dipole excitation. We discuss in some detail the behavior of
monopole and quadrupole modes as a function of boson-fermion coupling at
different boson-boson interaction strength. Analytic solutions valid at weak
and medium fermion-boson coupling are also derived and discussed.Comment: 29 pages + 7 figures, resubmitted to Physical Review
Control of Ultracold Collisions with Frequency-Chirped Light
We report on ultracold atomic collision experiments utilizing frequency-chirped laser light. A rapid
chirp below the atomic resonance results in adiabatic excitation to an attractive molecular potential over a
wide range of internuclear separation. This leads to a transient inelastic collision rate which is large
compared to that obtained with fixed-frequency excitation. The combination of high efficiency and
temporal control demonstrates the benefit of applying the techniques of coherent control to the ultracold
domain
Control of Ultracold Collisions with Frequency-Chirped Light
We report on ultracold atomic collision experiments utilizing frequency-chirped laser light. A rapid
chirp below the atomic resonance results in adiabatic excitation to an attractive molecular potential over a
wide range of internuclear separation. This leads to a transient inelastic collision rate which is large
compared to that obtained with fixed-frequency excitation. The combination of high efficiency and
temporal control demonstrates the benefit of applying the techniques of coherent control to the ultracold
domain
Control of Ultracold Collisions with Frequency-Chirped Light
We report on ultracold atomic collision experiments utilizing frequency-chirped laser light. A rapid
chirp below the atomic resonance results in adiabatic excitation to an attractive molecular potential over a
wide range of internuclear separation. This leads to a transient inelastic collision rate which is large
compared to that obtained with fixed-frequency excitation. The combination of high efficiency and
temporal control demonstrates the benefit of applying the techniques of coherent control to the ultracold
domain