14,088 research outputs found
Superfluid and insulating phases of fermion mixtures in optical lattices
The ground state phase diagram of fermion mixtures in optical lattices is
analyzed as a function of interaction strength, fermion filling factor and
tunneling parameters. In addition to standard superfluid, phase-separated or
coexisting superfluid/excess-fermion phases found in homogeneous or
harmonically trapped systems, fermions in optical lattices have several
insulating phases, including a molecular Bose-Mott insulator (BMI), a
Fermi-Pauli (band) insulator (FPI), a phase-separated BMI/FPI mixture or a
Bose-Fermi checkerboard (BFC). The molecular BMI phase is the fermion mixture
counterpart of the atomic BMI found in atomic Bose systems, the BFC or BMI/FPI
phases exist in Bose-Fermi mixtures, and lastly the FPI phase is particular to
the Fermi nature of the constituent atoms of the mixture.Comment: 4 pages with 3 figures (Published version
Magnetoresistive Effects in Ferromagnet-Superconductor Multilayers
We consider a nanoscale system consisting of Manganite-ferromagnet and
Cuprate-superconductor multilayers in a spin valve configuration. The
magnetization of the bottom Manganite-ferromagnet is pinned by a
Manganite-antiferromagnet. The magnetization of the top Manganite-ferromagnet
is coupled to the bottom one via indirect exchange through the superconducting
layers. We study the behavior of the critical temperature and the
magnetoresistance as a function of an externally applied parallel magnetic
field, when the number of Cuprate-superconductor layers are changed. There are
two typical behaviors in the case of a few monolayers of the Cuprates: a) For
small magnetic fields, the critical temperature and the magnetoresistance
change abruptly when the flipping field of the top Manganite-ferromagnet is
reached. b) For large magnetic fields, the multilayered system re-enters the
zero-resistance (superconducting) state after having become resistive (normal).Comment: 3 pages, 3 figures. 2004 Magnetism and Magnetic Materials Conferenc
Two-band superfluidity from the BCS to the BEC limit
We analyze the evolution of two-band superfluidity from the weak coupling
Bardeen-Cooper-Schrieffer (BCS) to the strong coupling Bose-Einstein
condensation (BEC) limit. When the interband interaction is tuned from negative
to positive values, a quantum phase transition occurs from a 0-phase to a
-phase state, depending on the relative phase of two order parameters.
Furthermore, population imbalances between the two bands can be created by
tuning the intraband or interband interactions. We also find two undamped low
energy collective excitations corresponding to in-phase and out-of-phase modes.
Lastly, we derive the coupled Ginzburg-Landau equations, and show that they
reduce to coupled Gross-Pitaevskii equations for two types of bosons in the BEC
limit.Comment: 4 pages and 3 figure
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