6 research outputs found
Dynamical control of matter-wave tunneling in periodic potentials
We report on measurements of dynamical suppression of inter-well tunneling of
a Bose-Einstein condensate (BEC) in a strongly driven optical lattice. The
strong driving is a sinusoidal shaking of the lattice corresponding to a
time-varying linear potential, and the tunneling is measured by letting the BEC
freely expand in the lattice. The measured tunneling rate is reduced and, for
certain values of the shaking parameter, completely suppressed. Our results are
in excellent agreement with theoretical predictions. Furthermore, we have
verified that in general the strong shaking does not destroy the phase
coherence of the BEC, opening up the possibility of realizing quantum phase
transitions by using the shaking strength as the control parameter.Comment: 5 pages, 3 figure
Observation of photon-assisted tunneling in optical lattices
We have observed tunneling suppression and photon-assisted tunneling of
Bose-Einstein condensates in an optical lattice subjected to a constant force
plus a sinusoidal shaking. For a sufficiently large constant force, the ground
energy levels of the lattice are shifted out of resonance and tunneling is
suppressed; when the shaking is switched on, the levels are coupled by
low-frequency photons and tunneling resumes. Our results agree well with
theoretical predictions and demonstrate the usefulness of optical lattices for
studying solid-state phenomena.Comment: 5 pages, 3 figure
AC-induced superfluidity
We argue that a system of ultracold bosonic atoms in a tilted optical lattice
can become superfluid in response to resonant AC forcing. Among others, this
allows one to prepare a Bose-Einstein condensate in a state associated with a
negative effective mass. Our reasoning is backed by both exact numerical
simulations for systems consisting of few particles, and by a theoretical
approach based on Floquet-Fock states.Comment: Accepted for publication in Europhysics letters, 6 pages, 4 figures,
Changes in v2: reference 7 replaced by a more recent on