2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session D16: Focus Session: BEC-BCS Crossover
2:30 PM–5:30 PM,
Monday, March 16, 2009
Room: 317
Sponsoring
Unit:
DAMOP
Chair: Kathy Levin, University of Chicago
Abstract ID: BAPS.2009.MAR.D16.1
Abstract: D16.00001 : BCS to BEC evolution for mixtures of fermions with unequal masses*
2:30 PM–3:06 PM
Preview Abstract
Abstract
Author:
Carlos A. R. Sa de Melo
(Georgia Institute of Technology)
I discuss the zero and finite temperature phase
diagrams of a mixture of fermions with unequal masses with and
without population imbalance, which may correspond for example to
mixtures of $^6$Li and $^{40}$K, $^6$Li and $^{87}$Sr, or
$^{40}$K and $^{87}$Sr in the context of ultracold atoms. At
zero temperature and when excess fermions are present, at least
three phases may occur as the interaction parameter is changed
from the BCS to the BEC regime. These phases correspond to
normal, phase separation, or superfluid with coexistence between
paired and excess fermions. The zero temperature phase diagram of
population imbalance versus interaction parameter presents a
remarkable asymmetry between the cases involving excess lighter
or heavier fermions [1, 2], in sharp contrast with the symmetric
phase diagram corresponding to the case of equal masses. At
finite temperatures, the phase separation region of the phase
diagram competes with superfluid regions possessing gapless
elementary excitations [3] for certain ranges of the interaction
parameter depending on the mass ratio. Furthermore, a phase
transition may take place between two superfluid phases which are
topologically distinct. The precise location of such transition
is sensitive to the mass ratio between the two species of
fermions. Signatures of this possible topological transition are
present in the momentum distribution or structure factor, which
may be measured experimentally in time-of-flight or through Bragg
scattering, respectively. Lastly, throughout the evolution from
BCS to BEC, I discuss the critical current and sound velocity for
unequal mass systems as a function of interaction parameter and
mass ratio. These quantities may also be measured via the same
techniques already used in mixtures of fermions with equal masses.
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[1] M. Iskin, and C. A. R. Sa de Melo, Phys. Rev. Lett. 97,
100404 (2006).
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[2] M. Iskin and C. A. R. Sa de Melo, Phys. Rev. A 76, 013601 (2007).
\newline
[3] Li Han, and C. A. R. Sa de Melo, arXiv:0812.xxxx
*Work supported by NSF (DMR-0709584).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.D16.1