论文标题
线性耦合的玻色子凝结物中的条纹和连接 - 涡流相
Stripe and junction-vortex phases in linearly coupled Bose-Einstein condensates
论文作者
论文摘要
在其理论预测之后不久，在合成旋转轨道偶联的存在下，条纹密度状态在超低中性原子的Bose-Einstein冷凝物中实现了[J.-R. Li等人，自然\ textbf {543}，91（2017）]。这项成就开放了探索超流体和结晶顺序的相互作用的途径，以寻找超胚膜特征和材料。所考虑的系统本质上是由两个线性耦合的Bose-Einstein冷凝物制成的，即伪旋转 - $ 1/2 $系统，受旋转依赖的量规场$σ_z\ hbar k_ \ ell $的约束。在这些条件下，当线性耦合$ \hbarΩ/2 $相对于量规能量$mΩ/\ hbar k_ \ ell^2 <1 $时，将实现条纹阶段。所得密度条纹已被解释为具有近似波数$ 2K_ \ ell $的内波干扰模式。在这里，我们表明条纹阶段的出现是由生活在线性耦合定义的连接处的一系列约瑟夫森涡流引起的。就像在受外部磁场的超导连接中发生的那样，涡流阵列是超流体系统对量规场的存在的自然响应。同样类似于超导体，在没有仪表场的情况下，约瑟夫森电流及其相关的涡旋可以作为亚稳态存在。我们为解释此类涡流阵列的1D平均场方程提供了封闭形式的解决方案。基础约瑟夫森电流与超导连接相对相的正弦戈登方程的分析溶液一致[C. C. Owen和D. Scalapino，物理。修订版\ textbf {164}，538（1967）]。
Soon after its theoretical prediction, striped-density states in the presence of synthetic spin-orbit coupling were realized in Bose-Einstein condensates of ultracold neutral atoms [J.-R. Li et al., Nature \textbf{543}, 91 (2017)]. The achievement opens avenues to explore the interplay of superfluidity and crystalline order in the search for supersolid features and materials. The system considered is essentially made of two linearly coupled Bose-Einstein condensates, that is a pseudo-spin-$1/2$ system, subject to a spin-dependent gauge field $σ_z \hbar k_\ell$. Under these conditions the stripe phase is achieved when the linear coupling $\hbarΩ/2$ is small against the gauge energy $mΩ/\hbar k_\ell^2<1$ . The resulting density stripes have been interpreted as a standing-wave, interference pattern with approximate wavenumber $2k_\ell$. Here, we show that the emergence of the stripe phase is induced by an array of Josephson vortices living in the junction defined by the linear coupling. As happens in superconducting junctions subject to external magnetic fields, a vortex array is the natural response of the superfluid system to the presence of a gauge field. Also similar to superconductors, the Josephson currents and their associated vortices can be present as a metastable state in the absence of gauge field. We provide closed-form solutions to the 1D mean field equations that account for such vortex arrays. The underlying Josephson currents coincide with the analytical solutions to the sine-Gordon equation for the relative phase of superconducting junctions [C. Owen and D. Scalapino, Phys. Rev. \textbf{164}, 538 (1967)].
