Yunbo Zhang

Shanxi University, Yangkü, Shanxi Sheng, China

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Publications (9)16.85 Total impact

  • Guanjun Chen · Li Chen · Yunbo Zhang
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    ABSTRACT: We present a variational study of the spin-1 Bose gases in a harmonic trap with three-dimensional spin-orbit coupling of Weyl type. For weak spin-orbit coupling, we treat the single-particle ground states as the form of perturbational harmonic oscillator states in the lowest total angular momentum manifold with $j=1, m_j=1,0,-1$. When the two-body interaction is considered, we set the trail order parameter as the superposition of three degenerate single-particle ground-states and the weight coefficients are determined by minimizing the energy functional. Two ground state phases, namely the magnetic and the nematic phases, are identified depending on the spin-independent and the spin-dependent interactions. Unlike the non-spin-orbit-coupled spin-1 Bose-Einstein condensate for which the phase boundary between the magnetic and the nematic phase lies exactly at zero spin-dependent interaction, the boundary is modified by the spin-orbit-coupling. We find the magnetic phase is featured with phase-separated density distributions, 3D skyrmion-like spin textures and competing magnetic and biaxial nematic orders, while the nematic phase is featured with miscible density distributions, zero magnetization and spatially modulated uniaxial nematic order. The emergence of higher spin order creates new opportunities for exploring spin-tensor-related physics in spin-orbit coupled superfluid.
    No preview · Article · Dec 2015
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    Tiantian Li · Su Yi · Yunbo Zhang
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    ABSTRACT: We investigate the ground-state and magnetic properties of a dipolar spin-1 Bose-Einstein condensate trapped in a symmetric double-well potential. In particular, we focus on the spin-vortex states by assuming that each potential well is highly pancake shaped. We show that the presence of the double-well potential gives rise to two different spin configurations for the spin-vortex pair states. We also study the response of the coupled spin-vortex pair to static transverse magnetic fields.
    Preview · Article · Dec 2015 · Physical Review A
  • Li Wang · Na Liu · Shu Chen · Yunbo Zhang
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    ABSTRACT: We investigate continuous-time quantum walks of two fermionic atoms loaded in one-dimensional optical lattices with on-site interaction and subjected to a Zeeman field. The quantum walks are accompanied by spin-flipping processes. We calculate the time-dependent density distributions of the two fermions with opposite spins which are initially positioned at the center site by means of an exact numerical method. Besides the usual fast linear expansion behavior, we find an interesting spin-flipping-induced localization in the time evolution of density distributions. We show that the fast linear expansion behavior can be restored by simply ramping up the Zeeman field or further increasing the spin-flipping strength. The intrinsic origin of this exotic phenomenon is attributed to the emergence of a flat band in the single-particle spectrum of the system. Furthermore, we investigate the effect of on-site interaction on the dynamics of the quantum walkers. The two-particle correlations are calculated and the signal of localization is also shown therein. A simple potential experimental application of this interesting phenomenon is proposed.
    No preview · Article · Nov 2015 · Physical Review A
  • Yanxia Liu · Yunbo Zhang
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    ABSTRACT: We propose to experimentally realize an odd-parity eigenstate $|b\ensuremath{\rangle}$ of two atoms in a double well. The occupation probability of this state shows evident dependence on the interaction, distinct from the result of two-mode model adopted in the Heidelberg experiment. The tunneling dynamics of two atoms starting from the NOON state with infinite barrier height can be derived from the exactly solved model of a $\ensuremath{\delta}$-barrier split double well based on a Bethe ansatz type hypothesis of the wave functions. We find that the single-particle tunneling shifts between the probability of double occupancy in the same well and that of single occupancy in different wells.
    No preview · Article · May 2015 · Physical Review A
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    Guanjun Chen · Tiantian Li · Yunbo Zhang
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    ABSTRACT: We present a variational study of pseudo-spin $1/2$ Bose gases in a harmonic trap with weak 3D spin-orbit coupling of $\bmsigma\cdot\mathbf{p}$ type. This spin-orbit coupling mixes states with different parities, which inspires us to approximate the single particle state with the eigenstates of the total angular momentum, i.e. superposition of harmonic $s$-wave and $p$-wave states. As the time reversal symmetry is protected by two-body interaction, we set the variational order parameter as the combination of two mutually time reversal symmetric eigenstates of the total angular momentum. The variational results essentially reproduce the 3D skyrmion-like ground state recently identified by Kawakami {\it et al.}. We show that these skyrmion-like ground states emerging in this model are primarily caused by $p$ wave spatial mode involving in the variational order parameter that drives two spin components spatially separated. We find the ground state of this system falls into two phases with different density distribution symmetries depending on the relative magnitude of intraspecies and interspecies interaction: Phase I has parity symmetric and axisymmetric density distributions, while Phase II is featured with special joint symmetries of discrete rotational and time reversal symmetry. With the increasing interaction strength the transition occurs between two phases with distinct density distributions, while the topological 3D skyrmion-like spin texture is symmetry protected.
    Preview · Article · Feb 2015
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    Yanxia Liu · Yunbo Zhang
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    ABSTRACT: We propose to experimentally realize an odd parity eigenstate $\left\vert b\right\rangle $ of two atoms in the double well. The occupation probability of this state shows evident dependence on the interaction, distinct from the result of two-mode model adopted in the Heidelberg experiment. The tunneling dynamics of two atoms starting from the $NOON$ state with infinite barrier height can be derived from the exactly solved model of $\delta $-barrier split double well based on a Bethe ansatz type hypothesis of the wave functions. We find that the single particle tunneling transfer the probabilities between double occupancy and single occupancy of each well.
    Preview · Article · Nov 2014
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    Limin Wang · Li Wang · Yunbo Zhang
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    ABSTRACT: We investigate continuous-time quantum walks of two indistinguishable anyons in one-dimensional lattices with both on-site and nearest-neighbor interactions based on the fractional Jordan-Wigner transformation. It is shown that the two-body correlations in position space are symmetric about the initial sites of two quantum walkers in the Bose limit ($\chi=0$ ) and Fermi limit ( $\chi=1$), while in momentum space this happens only in the Bose limit. An interesting asymmetry arises in the correlation for most cases with the statistical parameter $\chi$ varying in between. It turns out that the origin of this asymmetry comes from the fractional statistics that anyons obey. On the other hand, the two-body correlations of hard-core anyons in position spaceshow uniform behaviors from anti-bunching to co-walking regardless of the statistical parameter. The momentum correlations in the case of strong interaction undergo a smooth process of two stripes smoothly merging into a single one, i.e. the evolution of fermions into hard-core bosons.
    Preview · Article · Nov 2014 · Physical Review A
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    Yixiao Huang · Yunbo Zhang · Rong Lü · Xiaoguang Wang · Su Yi
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    ABSTRACT: We investigate the macroscopic quantum coherence of a spin-1 Rb condensate confined in an anisotropic potential. Under the single-mode approximation, we show that the system can be modeled as a biaxial quantum magnet due to the interplay between the magnetic dipole-dipole interaction and the anisotropic potential. By applying a magnetic field along the hard-axis, we show that the tunneling splitting oscillates as a function of the field strength. We also propose an experimental scheme to detect the oscillatory behavior of the tunneling splitting by employing the Landau-Zener tunneling.
    Full-text · Article · Jun 2012 · Physical Review A
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    L He · J. -N. Zhang · Yunbo Zhang · S. Yi
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    ABSTRACT: We investigate the stability and the free expansion of a trapped dipolar Fermi gas. We show that stabilizing the system relying on tuning the trap geometry is generally inefficient. We further show that the expanded density profile always gets stretched along the attractive direction of dipolar interaction. We also point out that by switching off the dipolar interaction simultaneously with the trapping potential, the deformation of momentum distribution can be directly observed. Comment: 5 pages, 5 figures
    Preview · Article · Nov 2007 · Physical Review A