Browsing by Subject "Order parameter"

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    Pairing and vortex lattices for interacting fermions in optical lattices with a large magnetic field
    (The American Physical Society, 2010) Zhai, H.; Umucalılar, R. O.; Oktel, M. Ö.
    We study the structure of a pairing order parameter for spin-1/2 fermions with attractive interactions in a square lattice under a uniform magnetic field. Because the magnetic translation symmetry gives a unique degeneracy in the single-particle spectrum, the pair wave function has both zero and finite-momentum components coexisting, and their relative phases are determined by a self-consistent mean-field theory. We present a microscopic calculation that can determine the vortex lattice structure in the superfluid phase for different flux densities. Phase transition from a Hofstadter insulator to a superfluid phase is also discussed.
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    Quantum entaglement and order parameter in a paired finite Fermi system
    (Elsevier Science, 2002-12) Gedik, Z.
    We study the pairing correlations in a finite Fermi system from the quantum entanglement point of view. We investigate the relation between the order parameter, which has been introduced recently to describe both finite and infinite superconductors, and the concurrence. For a proper definition of the concurrence, we argue that a possible generalization of the spin flip transformation is a time reversal operation. While for a system with indefinite number of particles concurrence is a good measure of entanglement, for a finite system it does not distinguish between normal and superconducting states. We propose that the expectation value of the radial operator for the total pseudospin can be used to identify entanglement of pairing.