Browsing by Author "Yin, Shaoyu"

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  • Fulde-Ferrell states and Berezinskii-Kosterlitz-Thouless phase transition in two-dimensional imbalanced Fermi gases
    (2014-01-01) Yin, Shaoyu; Martikainen, J.-P.; Törmä, Päivi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We study the superfluid properties of two-dimensional spin-population-imbalanced Fermi gases to explore the interplay between the Berezinskii-Kosterlitz-Thouless (BKT) phase transition and the possible instability towards the Fulde-Ferrell (FF) state. By the mean-field approximation together with quantum fluctuations, we obtain phase diagrams as functions of temperature, chemical potential imbalance, and binding energy. We find that the fluctuations change the mean-field phase diagram significantly. We also address possible effects of the phase separation and/or the anisotropic FF phase to the BKT mechanism. The superfluid density tensor of the FF state is obtained, and its transverse component is found always vanishing. This causes divergent fluctuations and possibly precludes the existence of the FF state at any nonzero temperature.
  • Superfluid phases of fermions with hybridized s and p orbitals
    (2015-11-17) Yin, Shaoyu; Baarsma, Jildou E.; Heikkinen, Miikka; Martikainen, Jani-Petri; Törmä, P.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We explore the superfluid phases of a two-component Fermi mixture with hybridized orbitals in optical lattices. We show that there exists a general mapping of this system to the Lieb lattice. By using simple multiband models with hopping between s- and p-orbital states, we show that superfluid order parameters can have a π-phase difference between lattice sites, which is distinct from the case with hopping between s orbitals. If the population imbalance between the two spin species is tuned, the superfluid phase may evolve through various phases due to the interplay between hopping, interactions, and imbalance. We show that the rich behavior is observable in experimentally realizable systems.