Dynamics of collapsing and exploding Bose-Einstein condensates

When atoms in a gas are cooled to extremely low temperatures, they will-und er the appropriate conditions-condense into a single quantum-mechanical sta te known as a Bose-Einstein condensate. In such systems, quantum-mechanical behaviour is evident on a macroscopic scale. Here we explore the dynamics of how a Bose-Einstein condensate collapses and subsequently explodes when the balance of forces governing its size and shape is suddenly altered. A c ondensate's equilibrium size and shape is strongly affected by the interato mic interactions. Our ability to induce a collapse by switching the interac tions from repulsive to attractive by tuning an externally applied magnetic field yields detailed information on the violent collapse process. We obse rve anisotropic atom bursts that explode from the condensate, atoms leaving the condensate in undetected forms, spikes appearing in the condensate wav efunction and oscillating remnant condensates that survive the collapse. Al l these processes have curious dependences on time, on the strength of the interaction and on the number of condensate atoms. Although the system woul d seem to be simple and well characterized, our measurements reveal many ph enomena that challenge theoretical models.