Superfluid-to-Mott-Insulating Transition

in a One-Dimensional Atomic Gas

Chad Fertig, Ken O’Hara, Johnny Huckans, Trey Porto and Bill Phillips

Laser Cooling and Trapping Group, Atomic Physics Division, Physics Laboratory

Over the past two decades, the Mott-insulating phase transition has received a great deal of attention as a prototypical example of a quantum phase transition in a strongly-correlated system for which quantum fluctuations drive the phase transition at zero temperature. The Mott transition is also of current interest due to its proximity to the superconducting state in high-temperature superconducting materials. We have observed the superfluid-to-Mott-insulating phase transition in an atomic gas by confining a Bose Einstein condensate in an optical lattice potential. The Mott insulating state arises due to strong repulsive interactions between the particles that reduce number fluctuations on the lattice sites, inhibiting particle mobility and reducing phase coherence across the sample.

We realize the Mott insulating state in a one-dimensional system by initially confining a Bose-Einstein condensate in a two-dimensional optical lattice, producing an array of one-dimensional tubes. An additional optical lattice potential is then applied adiabatically along the axis of the tubes. As the superfluid-to-insulating phase transition is crossed, a loss of phase coherence is observed, indicated by a reduced visibility of atomic Bragg diffraction peaks. In one-dimension, strong correlations between the particles exist even before the lattice potential is applied which may make the transition particularly robust. We have also explored transport properties in this system, observing strongly damped oscillations at surprisingly low depths of the lattice potential. We are interested in using the Mott transition as a method to initialize a quantum register with exactly one atom per lattice site. This will enable future experiments with quantum information processing that use the internal states of neutral atoms as quantum bits.

Name:Chad Fertig Name: Ken O’Hara

Division: Atomic Physics Division: Atomic Physics

Laboratory: Physics Laboratory: Physics

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Sigma Xi member?:No Sigma Xi member? No

Category:Physics Category: Physics