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Article Dans Une Revue Physical Review A : Atomic, molecular, and optical physics [1990-2015] Année : 2004

Limits of sympathetic cooling of fermions by zero temperature bosons due to particle losses

Lincoln D. Carr
  • Fonction : Auteur
Thomas Bourdel
Yvan Castin

Résumé

It has been suggested by Timmermans [Phys. Rev. Lett. {\bf 87}, 240403 (2001)] that loss of fermions in a degenerate system causes strong heating. We address the fundamental limit imposed by this loss on the temperature that may be obtained by sympathetic cooling of fermions by bosons. Both a quantum Boltzmann equation and a quantum Boltzmann \emph{master} equation are used to study the evolution of the occupation number distribution. It is shown that, in the thermodynamic limit, the Fermi gas cools to a minimal temperature $k_{{\rm B}}T/\mu\propto(\gamma_{{\rm loss}}/\gamma_{{\rm coll}})^{0.44}$, where $\gamma_{{\rm loss}}$ is a constant loss rate, $\gamma_{{\rm coll}}$ is the bare fermion--boson collision rate not including the reduction due to Fermi statistics, and $\mu\sim k_{{\rm B}}T_{{\rm F}}$ is the chemical potential. It is demonstrated that, beyond the thermodynamic limit, the discrete nature of the momentum spectrum of the system can block cooling. The unusual non-thermal nature of the number distribution is illustrated from several points of view: the Fermi surface is distorted, and in the region of zero momentum the number distribution can descend to values significantly less than unity. Our model explicitly depends on a constant evaporation rate, the value of which can strongly affect the minimum temperature.

Dates et versions

hal-00002441 , version 1 (03-08-2004)

Identifiants

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Lincoln D. Carr, Thomas Bourdel, Yvan Castin. Limits of sympathetic cooling of fermions by zero temperature bosons due to particle losses. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2004, 69, pp.033603. ⟨hal-00002441⟩
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