1,041 research outputs found
Zero-temperature phase diagram of Yukawa bosons
We study the zero-temperature phase diagram of bosons interacting via
screened Coulomb (Yukawa) potential by means of the diffusion Monte Carlo
method. The Yukawa potential is used as a model interaction in the neutron
matter, dusty plasmas and charged colloids. As shown by D. S. Petrov et al.
[Phys. Rev. Lett. 99, 130407 (2007)], interactions between weakly bound
molecules of heavy and light fermionic atoms are described by an effective
Yukawa potential with a strength related to the heavy-light mass ratio M/m
which might lead to crystallization in a two-dimensional geometry if the mass
ratio of heavy-light fermions exceeds a certain critical value. In the present
work we do a thorough study of the quantum three-dimensional Yukawa system. For
strong interactions (equivalently, large mass ratios) the system experiences
several phase transitions as the density is increased, passing from gas to
solid and to gas phase again. Weakly interacting Yukawa particles do not
crystallize at any density. We find the minimal interaction strength at which
the crystallization happens. In terms of the two-component fermionic system,
this strength corresponds to a heavy-light mass ratio of M/m ~ 180, so that it
is impossible to realize the gas-crystal transition in a conventional bulk
system. For the Yukawa model of fermionic mixtures we also analyze the
possibility of building molecular systems with very large effective mass ratios
by confining the heavy component to a sufficiently deep optical lattice. We
show how the effective mass of the heavy component can be made arbitrarily
large by increasing the lattice depth, thus leading to a tunable effective mass
ratio that can be used to realize a molecular superlattice.Comment: added figure with finite-size dependence of the energy; comments and
references added; title change
Liberating Efimov physics from three dimensions
When two particles attract via a resonant short-range interaction, three
particles always form an infinite tower of bound states characterized by a
discrete scaling symmetry. It has been considered that this Efimov effect
exists only in three dimensions. Here we review how the Efimov physics can be
liberated from three dimensions by considering two-body and three-body
interactions in mixed dimensions and four-body interaction in one dimension. In
such new systems, intriguing phenomena appear, such as confinement-induced
Efimov effect, Bose-Fermi crossover in Efimov spectrum, and formation of
interlayer Efimov trimers. Some of them are observable in ultracold atom
experiments and we believe that this study significantly broadens our horizons
of universal Efimov physics.Comment: 17 pages, 5 figures, contribution to a special issue of Few-Body
Systems devoted to Efimov Physic
Feshbach spectroscopy and analysis of the interaction potentials of ultracold sodium
We have studied magnetic Feshbach resonances in an ultracold sample of Na
prepared in the absolute hyperfine ground state. We report on the observation
of three s-, eight d-, and three g-wave Feshbach resonances, including a more
precise determination of two known s-wave resonances, and one s-wave resonance
at a magnetic field exceeding 200mT. Using a coupled-channels calculation we
have improved the sodium ground-state potentials by taking into account these
new experimental data, and derived values for the scattering lengths. In
addition, a description of the molecular states leading to the Feshbach
resonances in terms of the asymptotic-bound-state model is presented.Comment: 11 pages, 4 figure
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