We study quantum dynamical properties of a spin-1 atomic Bose-Einstein condensate in a double-well potential. Adopting a mean field theory and single spatial mode approximation, we characterize our model system as two coupled spins. For certain initial states, we find full magnetization oscillations between wells not accompanied by mass (or atom numbers) exchange. We identify dynamic regimes of collective spin variables arising from nonlinear self-interactions that are different from the usual Josephson oscillations. We also discuss magnetization beats and incomplete oscillations of collective spin variables other than the magnetization. Our study points to an alternative approach to observe coherent tunnelling of a condensate through a (spatial) potential barrier.
We study the emergence of hysteresis during the process of quantum phase transition from an antiferromagnetic to a phase-separated state in a spin-1 Bose Einstein condensate of ultracold atoms. We explicitly demonstrate the appearance of a hysteresis loop with various quench times showing that it is rate-independent for large magnetizations only. In other cases scaling of the hysteresis loop area is observed, which we explain by using the Kibble-Zurek theory in the limit of small magnetization. The effect of an external harmonic trapping potential is also discussed.
We study the effect of an external harmonic trapping potential on an outcome of the non-adiabatic quantum phase transition from an antiferromagnetic to a phase-separated state in a spin-1 atomic condensate. Previously, we demonstrated that the dynamics of an untrapped system exhibits double universality with two different scaling laws appearing due to conservation of magnetization. We show that in the presence of a trap double universality persists. However, the corresponding scaling exponents are strongly modified by transfer of local magnetization across the system. The values of these expon…
We consider an antiferromagnetic Bose-Einstein condensate in a traverse magnetic field with a fixed macroscopic magnetization. The system exhibits two different critical behaviors corresponding to transitions from polar to broken-axisymmetry and from antiferromagnetic to broken-axisymmetry phases depending on the value of magnetization. We exploit both types of system criticality as a resource in the precise estimation of control parameter value. We quantify the achievable precision by the quantum Fisher information. We demonstrate supersensitivity and show that the precision scales with the n…
Edge binding of sine-Gordon solitons in spin-orbit coupled Bose-Einstein condensates
在最近的超冷气体实验中，拉曼耦合方案用于产生自旋轨道（SO）和塞曼型耦合[Y. J. Lin等人，Nature 471，83（2011）]。它们的竞争驱动相变到具有破缺的$Z_2$对称性的磁化状态。使用流体动力学方法，我们研究了一个封闭的二元冷凝物受到SO和塞曼型耦合。我们发现，在小愈合长度的限制下，在对称性未破缺的相位中，边界磁化分布具有正弦-戈登孤子形式的解析解。孤子被束缚到系统的边缘的非平凡的边界条件所产生的SO耦合和粒子密度下降的综合影响。同样的边界条件是重要的磁化阶段，以及，在那里我们的特征数值边界自旋结构。我们进一步讨论了非平凡的磁化结构如何影响边界附近的密度分布，这是另一个可以在当前的自旋轨道耦合凝聚体实验中进行测试的预测。
The spinor condensate with spin states degenerated in the ground spin-space provides a unique platform for investigating the edge of quantum mechanics and statistical physics. We study the evolution of the condensate under the scattering of a coherent atom beam. The time-dependent magnetization, entanglement entropy, thermal entropy and the entropy production rate are calculated. A novel spontaneous symmetry breaking is found during the evolution, It is shown that the stationary spin distribution can be controlled by the incoming coherent spin state of the incident atom beam, therefore the ato…
