SEMINAIRE MERCREDI 1 SEPTEMBRE 2004
14 heures
Salle Séminaire 5
Centre de Physique Théorique
Marseille-Luminy

Robert Seiringer
Princeton University

Title: Bose-Einstein Quantum Phase Transition in Optical Lattice Model

Abstract: Bose-Einstein condensation (BEC) in cold gases can be turned on and off
by an external potential, such as that presented by an optical lattice. We present
a model of this phenomenon which we are able to analyze rigorously. The system is a
hard core lattice gas at half-filling and the optical lattice is modeled by a
periodic potential of strength \lambda. For small \lambda and temperature, BEC is
proved to occur, while at large \lambda or temperature there is no BEC. At large
\lambda the low-temperature states are in a Mott insulator phase with a
characteristic gap that is absent in the BEC phase. The interparticle interaction
is essential for this transition, which occurs even in the ground state.
Surprisingly, the condensation is always into the p=0 mode in this model, although
the density itself has the periodicity of the imposed potential.

See: arXiv:cond-mat/0403240

In collaboration with: Michael Aizenman, Elliott H. Lieb, Jan Philip Solovej,
Jakob Yngvason