Phases of a Two-Dimensional Bose Gas in an Optical Lattice

Karina’s paper [Phys. Rev. Lett. 105, 110401 (2010)] featuring a fantastic measurement of the SF/MI phase transition in a 2D Bose-Hubbard system has been published in PRL.  Our result is in agreement with QMC calculations with no adjustable parameters.

This work is featured on the JQI site.

Abstract: Ultracold atoms in optical lattices realize simple condensed matter models. We create an ensemble of ≈60 harmonically trapped 2D Bose-Hubbard systems from a ⁸⁷Rb Bose-Einstein condensate in an optical lattice and use a magnetic resonance imaging approach to select a few 2D systems for study, thereby eliminating ensemble averaging. Our identification of the transition from superfluid to Mott insulator, as a function of both atom density and lattice depth, is in excellent agreement with a universal state diagram [M. Rigol et al. Phys. Rev. A 79 053605 (2009)] suitable for our trapped system. In agreement with theory, our data suggest a failure of the local density approximation in the transition region.