Coherent decay of Bose-Einstein condensates

As the coldest form of matter known to exist, atomic Bose-Einstein condensates are unique forms of matter where the constituent atoms lose their individual identities, becoming absorbed into the cloud as a whole. Effectively, these gases become a single macroscopic object that inherits its properties directly from the quantum world. In this work, I describe the quantum properties of a zero temperature condensate where the atoms have a propensity to pair, thereby leading to a molecular character that coexists with the atoms. Remarkably, the addition of this molecular component is found to induce a quantum instability that manifests itself as a collective decay of the assembly as a whole. As a signature of this phenomenon, there arises a complex chemical potential in which the imaginary part quantifies a coherent decay into collective phonon excitations of a collapsing ground state. The unique decay rate dependencies on both the scattering length and the density can be experimentally tested by tuning near a Feshbach resonance. Being a purely quantum mechanical effect, there exists no mechanical picture corresponding to this coherent many-body process. The results presented can serve as a model for other systems with similar underlying physics.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Cragg, George E. (George Edwin), 1972-

Advisor dc:contributor.advisor

• Arthur K. Kerman.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/35304

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/35304