Condensed Matter Physics Seminar

2D Bosons in an optical lattice: an experimental study

Dr. Ian Spielman
NIST
Tuesday, April 4, 2006
Higgins 235, 3pm

Ultra-cold atoms confined to optical lattices are a unique condensed
matter system. I will discuss the case of 2D Bose systems, where the
atoms are free to move in two directions, but strongly confined in the
third.

Bose-condensed rubidium atoms are loaded into a 3D optical lattice
with an average occupancy of one atom per-site. An ensemble of 2D
lattice systems are realized when one direction of the 3D lattice is
much deeper than the remaining two. These 2D systems exhibit a
superfluid-insulator transition as the lattice depth (in the remaining
2 directions) is increased. I present new measurements that show that
the conventional signature of long-range order, namely diffraction,
disappears continuously as the Mott state develops, likewise the
coherence-length continuously decreases. We also probe this
transition via correlations in atom shot noise in a manner which is
sensitive only to atoms in the Mott state.