43 research outputs found
Narrow Line Photoassociation in an Optical Lattice
With ultracold Sr in a 1D magic wavelength optical lattice, we
performed narrow line photoassociation spectroscopy near the SP intercombination transition. Nine least-bound vibrational molecular
levels associated with the long-range and potential energy surfaces
were measured and identified. A simple theoretical model accurately describes
the level positions and treats the effects of the lattice confinement on the
line shapes. The measured resonance strengths show that optical tuning of the
ground state scattering length should be possible without significant atom
loss.Comment: 4 pages, 4 figure
Coherent transfer of photoassociated molecules into the rovibrational ground state
We report on the direct conversion of laser-cooled 41K and 87Rb atoms into
ultracold 41K87Rb molecules in the rovibrational ground state via
photoassociation followed by stimulated Raman adiabatic passage.
High-resolution spectroscopy based on the coherent transfer revealed the
hyperfine structure of weakly bound molecules in an unexplored region. Our
results show that a rovibrationally pure sample of ultracold ground-state
molecules is achieved via the all-optical association of laser-cooled atoms,
opening possibilities to coherently manipulate a wide variety of molecules.Comment: 4 pages, 4 figure
Demkov-Kunike model for cold atom association: weak interaction regime
We study the nonlinear mean-field dynamics of molecule formation at coherent
photo- and magneto-association of an atomic Bose-Einstein condensate for the
case when the external field configuration is defined by the quasi-linear level
crossing Demkov-Kunike model, characterized by a bell-shaped pulse and finite
variation of the detuning. We present a general approach to construct an
approximation describing the temporal dynamics of the molecule formation in the
weak interaction regime and apply the developed method to the nonlinear
Demkov-Kunike problem. The presented approximation, written as a scaled
solution to the linear problem associated to the nonlinear one we treat,
contains fitting parameters which are determined through a variational
procedure. Assuming that the parameters involved in the solution of the linear
problem are not modified, we suggest an analytical expression for the scaling
parameter.Comment: 6 pages, 4 figure
Efimov physics beyond three particles
Efimov physics originally refers to a system of three particles. Here we
review recent theoretical progress seeking for manifestations of Efimov physics
in systems composed of more than three particles. Clusters of more than three
bosons are tied to each Efimov trimer, but no independent Efimov physics exists
there beyond three bosons. The case of a few heavy fermions interacting with a
lighter atom is also considered, where the mass ratio of the constituent
particles plays a significant role. Following Efimov's study of the (2+1)
system, the (3+1) system was shown to have its own critical mass ratio to
become Efimovian. We show that the (4+1) system becomes Efimovian at a mass
ratio which is smaller than its sub-systems thresholds, giving a pure five-body
Efimov effect. The (5+1) and (6+1) systems are also discussed, and we show the
absence of 6- and 7-body Efimov physics there
Efimov Trimers near the Zero-crossing of a Feshbach Resonance
Near a Feshbach resonance, the two-body scattering length can assume any
value. When it approaches zero, the next-order term given by the effective
range is known to diverge. We consider the question of whether this divergence
(and the vanishing of the scattering length) is accompanied by an anomalous
solution of the three-boson Schr\"odinger equation similar to the one found at
infinite scattering length by Efimov. Within a simple zero-range model, we find
no such solutions, and conclude that higher-order terms do not support Efimov
physics.Comment: 8 pages, no figures, final versio
Efimov physics from the functional renormalization group
Few-body physics related to the Efimov effect is discussed using the
functional renormalization group method. After a short review of
renormalization in its modern formulation we apply this formalism to the
description of scattering and bound states in few-body systems of identical
bosons and distinguishable fermions with two and three components. The Efimov
effect leads to a limit cycle in the renormalization group flow. Recently
measured three-body loss rates in an ultracold Fermi gas Li atoms are
explained within this framework. We also discuss briefly the relation to the
many-body physics of the BCS-BEC crossover for two-component fermions and the
formation of a trion phase for the case of three species.Comment: 28 pages, 13 figures, invited contribution to a special issue of
"Few-Body Systems" devoted to Efimov physics, published versio
Weak coupling regime of the Landau-Zener transition for association of an atomic Bose-Einstein condensate
In the framework of a basic semiclassical time-dependent nonlinear two-state
problem, we study the weak coupling limit of the nonlinear Landau-Zener
transition at coherent photo- and magneto-association of an atomic
Bose-Einstein condensate. Using an exact third-order nonlinear differential
equation for the molecular state probability, we develop a variational approach
which enables us to construct an accurate analytic approximation describing
time dynamics of the coupled atom-molecular system for the case of weak
coupling. The approximation is written in terms of the solution to an auxiliary
linear Landau-Zener problem with some effective Landau-Zener parameter. The
dependence of this effective parameter on the input Landau-Zener parameter is
found to be unexpected: as the generic Landau-Zener parameter increases, the
effective Landau-Zener parameter first monotonically increases (starting from
zero), reaches its maximal value and then monotonically decreases again
reaching zero at some point. The constructed approximation quantitatively well
describes many characteristics of the time dynamics of the system, in
particular, it provides a highly accurate formula for the final transition
probability to the molecular state. The present result for the final transition
probability improves the accuracy of the previous approximation by Ishkhanyan
et al. [Phys. Rev. A 69, 043612 (2004); J. Phys. A 38, 3505 (2005)] by order of
magnitude.Comment: 7 pages, 3 figure
Universal clusters as building blocks of stable quantum matter
We present an exploratory study that suggests that Efimov physics, a leading
research theme in few-body quantum physics, can also induce stable many-body
ground states whose building blocks are universal clusters. We identify a range
of parameters in a mass-and-density imbalanced two-species fermionic mixture
for which the ground state is a gas of Efimov-related universal trimers. An
explicit calculation of the trimer-trimer interaction reveals that the trimer
phase is an SU Fermi liquid stable against recombination losses. We
propose to experimentally observe this phase in a fermionic Li-Cr
mixture.EPSRC (Grant ID: EP/I004637/1)This is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevA.93.05361