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

Abstract

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.

Authors:
; ;  [1]
  1. Department of Physics, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan)
Publication Date:
OSTI Identifier:
20982575
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.75.053615; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Shibata, Hiroyuki, Yokoshi, Nobuhiko, and Kurihara, Susumu. Collective modes and stability of Bose-Fermi mixtures with a BCS-BEC crossover. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.053615.
Shibata, Hiroyuki, Yokoshi, Nobuhiko, & Kurihara, Susumu. Collective modes and stability of Bose-Fermi mixtures with a BCS-BEC crossover. United States. doi:10.1103/PHYSREVA.75.053615.
Shibata, Hiroyuki, Yokoshi, Nobuhiko, and Kurihara, Susumu. Tue . "Collective modes and stability of Bose-Fermi mixtures with a BCS-BEC crossover". United States. doi:10.1103/PHYSREVA.75.053615.
@article{osti_20982575,
title = {Collective modes and stability of Bose-Fermi mixtures with a BCS-BEC crossover},
author = {Shibata, Hiroyuki and Yokoshi, Nobuhiko and Kurihara, Susumu},
abstractNote = {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.},
doi = {10.1103/PHYSREVA.75.053615},
journal = {Physical Review. A},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}