Bose Gases Near Unitarity

Abstract

We study the properties of strongly interacting Bose gases at the density and temperature regime when the three-body recombination rate is substantially reduced. In this regime, one can have a Bose gas with all particles in scattering states (i.e. the "upper branch") with little loss even at unitarity over the duration of the experiment. We show that because of bosonic enhancement, pair formation is shifted to the atomic side of the original resonance (where scattering length $a_s<0$), opposite to the fermionic case. In a trap, a repulsive Bose gas remains mechanically stable when brought across resonance to the atomic side until it reaches a critical scattering length $a_s^{\ast }<0$. For $a_s<a_s^{\ast }$, the density consists of a core of upper branch bosons surrounded by an outer layer of equilibrium phase. The conditions of low three-body recombination requires that the particle number $N<\alpha (T/\omega {)}^{5/2}$ in a harmonic trap with frequency $\omega$, where $\alpha$ is a constant.

4 pages, 4 figures

References in corpus (7)

• Theory of ultracold Fermi gases
• Universality in Three- and Four-Body Bound States of Ultracold Atoms
• Itinerant Ferromagnetism in a Fermi Gas of Ultracold Atoms
• Competition between pairing and ferromagnetic instabilities in ultracold Fermi gases near Feshbach resonances
• Limits on Universality in Ultracold Three-Boson Recombination
• Atom Loss Maximum in Ultra-cold Fermi Gases
• The Nature and Properties of a Repulsive Fermi Gas in the "Upper Branch"

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• Monte Carlo Simulations of the Unitary Bose Gas
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