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Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

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Coherent decay of Bose-Einstein condensates.

George E Cragg¹, Arthur K Kerman

¹Los Alamos National Laboratory, Los Alamos, NM 87545, USA.

Physical Review Letters

|March 16, 2007

Summary

Atomic Bose-Einstein condensates exhibit losses explained by a new theory linking decay rates to interparticle interactions. This model reveals a novel density dependence, improving understanding of these quantum states.

Area of Science:

Quantum physics
Atomic physics
Condensed matter physics

Background:

Atomic Bose-Einstein condensates (BECs) are quantum states of matter characterized by atomic coherence.
Observed losses in BECs are traditionally explained by classical collision models.
A deeper understanding of microscopic interactions is needed to explain BEC decay.

Purpose of the Study:

To develop a theoretical framework linking BEC losses to microscopic interparticle interactions.
To derive a coherent decay rate from a general interparticle interaction Hamiltonian.
To investigate the density dependence of decay rates in BECs.

Main Methods:

Incorporation of a general interparticle interaction into the Hamiltonian.
Derivation of a coherent decay rate.

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Analysis of the interaction strength (lambda) and its relation to experimental data.

Identification of density dependence in the lowest order decay rate.

Main Results:

A direct link between observed BEC losses and microscopic two-body parameters was established.
The interaction strength lambda was expressed in terms of atomic properties and a fitting parameter delta.
A novel density dependence of the decay rate, proportional to rho{3/2}, was identified.
The parameter delta was determined by fitting the model to experimental loss data.

Conclusions:

The study provides a microscopic explanation for losses in atomic Bose-Einstein condensates.
The derived coherent decay rate offers a more accurate description than classical models.
The predicted rho{3/2} density dependence serves as a testable signature for low-temperature experiments.