Motivated by a goal of realizing spin-orbit coupling (SOC) beyond one-dimension (1D), we propose and analyze a method to generate an effective 2D SOC in bilayer BECs with laser-assisted inter-layer tunneling. We show that an interplay between the int
er-layer tunneling, SOC and intra-layer atomic interaction can give rise to diverse ground state configurations. In particular, the system undergoes a transition to a new type of stripe phase which spontaneously breaks the time-reversal symmetry. Different from the ordinary Rashba-type SOC, a fractionalized skyrmion lattice emerges spontaneously in the bilayer system without external traps. Furthermore, we predict the occurrence of a tetracritical point in the phase diagram of the bilayer BECs, where four different phases merge together. The origin of the emerging different phases is elucidated.
We investigate the superfluidity of attractive Fermi gas in a square optical lattice with spin-orbit coupling (SOC). We show that the system displays a variety of new filling-dependent features. At half filling, a quantum phase transition from a semi
metal to a superfluid is found for large SOC. Close to half filling where the emerging Dirac cones governs the behaviors of the system, SOC tends to suppress the BCS superfluidity. Conversely, SOC can significantly enhance both the pairing gap and condensate fraction and lead to a new BCS-BEC crossover for small fillings. Moreover, we demonstrate that the superfluid fraction also exhibits many interesting phenomena compared with the spin-orbit coupled Fermi gas without lattice.
We point out that the widely accepted condition g11g22<g122 for phase separation of a two-component Bose-Einstein condensate is insufficient if kinetic energy is taken into account, which competes against the intercomponent interaction and favors pha
se mixing. Here g11, g22, and g12 are the intra- and intercomponent interaction strengths, respectively. Taking a d-dimensional infinitely deep square well potential of width L as an example, a simple scaling analysis shows that if d=1 (d=3), phase separation will be suppressed as Lrightarrow0 (Lrightarrowinfty) whether the condition g11g22<g122 is satisfied or not. In the intermediate case of d=2, the width L is irrelevant but again phase separation can be partially or even completely suppressed even if g11g22<g122. Moreover, the miscibility-immiscibility transition is turned from a first-order one into a second-order one by the kinetic energy. All these results carry over to d-dimensional harmonic potentials, where the harmonic oscillator length {xi}ho plays the role of L. Our finding provides a scenario of controlling the miscibility-immiscibility transition of a two-component condensate by changing the confinement, instead of the conventional approach of changing the values of the gs.
Recent discovery of several overluminous type Ia supernovae (SNe Ia) indicates that the explosive masses of white dwarfs may significantly exceed the canonical Chandrasekhar mass limit. Rapid differential rotation may support these massive white dwar
fs. Based on the single-degenerate scenario, and assuming that the white dwarfs would differentially rotate when the accretion rate $dot{M}>3times 10^{-7}M_{odot}rm yr^{-1}$, employing Eggletons stellar evolution code we have performed the numerical calculations for $sim$ 1000 binary systems consisting of a He star and a CO white dwarf (WD). We present the initial parameters in the orbital period - helium star mass plane (for WD masses of $1.0 M_{odot}$ and $1.2 M_{odot}$, respectively), which lead to super-Chandrasekhar mass SNe Ia. Our results indicate that, for an initial massive WD of $1.2 M_{odot}$, a large number of SNe Ia may result from super-Chandrasekhar mass WDs, and the highest mass of the WD at the moment of SNe Ia explosion is 1.81 $M_odot$, but very massive ($>1.85M_{odot}$) WDs cannot be formed. However, when the initial mass of WDs is $1.0 M_{odot}$, the explosive masses of SNe Ia are nearly uniform, which is consistent with the rareness of super-Chandrasekhar mass SNe Ia in observations.
