Collective modes and stability of Bose-Fermi mixtures with a BCS-BEC crossover

Journal Article · Tue May 15 04:00:00 EDT 2007 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.75.053615· OSTI ID:20982575

Shibata, Hiroyuki; Yokoshi, Nobuhiko; Kurihara, Susumu ^[1]

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1. Department of Physics, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan)

We investigate an ultracold Bose-Fermi mixture with a Feshbach resonance between two hyperfine states of fermions. Using a functional integral method, we calculate collective modes associated with fermion pairs and bosons in the superfluid phase. We derive a stability condition of the mixtures that is valid in the entire region of the BCS-BEC crossover. This stability condition, which smoothly connects the well-known results obtained in both the BCS and Bose-Einstein Condensate (BEC) limits, shows that sufficiently strong fermion-boson (FB) interactions destabilize the mixtures. In order to investigate the consequence of this instability, we study the ground-state energy of both the uniformly mixed and the phase-separated states. We find that FB repulsion induces a phase separation, whereas FB attraction should cause a collapse of the mixture. The possibilities for the experimental observation of such instabilities are also discussed.

• OSTI ID: 20982575
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 5 Vol. 75; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BCS THEORY
BOSE-EINSTEIN CONDENSATION
BOSE-EINSTEIN GAS
BOSONS
FERMI GAS
FERMIONS
GROUND STATES
INSTABILITY
INTERACTIONS
MIXTURES
RESONANCE
STABILITY
SUPERFLUIDITY