Browsing by Author "Zhang, Yong-Chang"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Stable Solitons in Three Dimensional Free Space without the Ground State: Self-Trapped Bose-Einstein Condensates with Spin-Orbit Coupling
    (American Physical Society, 2015) Zhang, Yong-Chang; Zhou, Zheng-Wei; Malomed, Boris A.; Pu, Han; Rice Center for Quantum Materials
    By means of variational methods and systematic numerical analysis, we demonstrate the existence of metastable solitons in three dimensional (3D) free space, in the context of binary atomic condensates combining contact self-attraction and spin-orbit coupling, which can be engineered by available experimental techniques. Depending on the relative strength of the intra- and intercomponent attraction, the stable solitons feature a semivortex or mixed-mode structure. In spite of the fact that the local cubic self-attraction gives rise to the supercritical collapse in 3D, and hence the setting produces no true ground state, the solitons are stable against small perturbations, motion, and collisions.
  • Thumbnail Image
    Item
    Two-component Bose-Hubbard model in an array of cavity polaritons
    (American Physical Society, 2015) Zhang, Yong-Chang; Zhou, Xiang-Fa; Zhou, Xingxiang; Guo, Guang-Can; Pu, Han; Zhou, Zheng-Wei
    We propose a scheme which can realize an extended two-component Bose-Hubbard model using polaritons confined in an array of optical cavities. In addition to the density-dependent interactions, this model also contains nonlinear coupling terms between the two components of the polariton. Using a mean-field calculation, we obtain the phase diagram which shows how these terms affect the transition between the Mott insulator and the superfluid phase. In addition, we employ both a perturbation approach and an exact diagonalization method to gain more insights into the phase diagram.
  • Thumbnail Image
    Item
    Two-component polariton condensate in an optical microcavity
    (American Physical Society, 2014) Zhang, Yong-Chang; Zhou, Xiang-Fa; Guo, Guang-Can; Zhou, Xingxiang; Pu, Han; Zhou, Zheng-Wei; Rice Quantum Institute
    We present a scheme for engineering the extended two-component Bose-Hubbard model using polariton condensate supported by an optical microcavity. Compared to the usual two-component Bose-Hubbard model with only Kerr nonlinearity, our model includes a nonlinear tunneling term which depends on the number difference of the particle in the two modes. In the mean-field treatment, this model is an analog to a nonrigid pendulum with a variable pendulum length whose sign can be also changed. We study the dynamic and groundstate properties of this model and show that there exists a first-order phase transition as the strength of the nonlinear tunneling rate is varied. Furthermore, we propose a scheme to obtain the polariton condensate wave function.