799 research outputs found
Exotic roton excitations in quadrupolar Bose-Einstein condensates
We investigate the occurrence of rotons in a quadrupolar Bose-Einstein
condensate confined to two dimensions. Depending on the particle density, the
ratio of the contact and quadrupole-quadrupole interactions, and the alignment
of the quadrupole moments with respect to the confinement plane, the dispersion
relation features two or four point-like roton minima, or one ring-shaped
minimum. We map out the entire parameter space of the roton behavior and
identify the instability regions. We propose to observe the exotic rotons by
monitoring the characteristic density wave dynamics resulting from a short
local perturbation, and discuss the possibilities to detect the predicted
effects in state-of-the-art experiments with ultracold homonuclear molecules
Detecting paired and counterflow superfluidity via dipole oscillations
We suggest an experimentally feasible procedure to observe paired and
counterflow superfluidity in ultra-cold atom systems. We study the time
evolution of one-dimensional mixtures of bosonic atoms in an optical lattice
following an abrupt displacement of an additional weak confining potential. We
find that the dynamic responses of the paired superfluid phase for attractive
inter-species interactions and the counterflow superfluid phase for repulsive
interactions are qualitatively distinct and reflect the quasi long-range order
that characterizes these states. These findings suggest a clear experimental
procedure to detect these phases, and give an intuitive insight into their
dynamics.Comment: 4 pages,5 figure
Mixing-Demixing transition in 1D boson-fermion mixture at low fermion densities
We numerically investigated the mixing-demixing transition of the
boson-fermion mixture on a 1D lattice at an incommensurate filling with the
fermion density being kept below the boson density. The phase diagram we
obtained suggested that the decrease of the number of the fermions drove the
system into the demixing phase
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