论文标题
伸长的偶极bose-Einstein冷凝物中的激发和数量波动
Excitations and number fluctuations in an elongated dipolar Bose-Einstein condensate
论文作者
论文摘要
我们研究磁性偶极bose-Einstein冷凝物（BEC）在伸长（雪茄形的）限制电位中的特性。在该系统中，偶极 - 偶极相互作用（DDIS）产生了与偶极子的横向限制和极化方向相关的动量依赖性。这会导致密度波动在与横向限制长度有关的长度尺度上得到增强或抑制，而局部原子数测量是在实验中观察这些效应的实际方法。我们使用曲折理论来描述基态，激发和局部数量波动。定量预测是根据完整的数值解决方案和我们开发的简化变分方法提出的。除了众所周知的Roton激发外，当偶极子沿着紧密狭窄的方向极化时，我们还发现了沿长轴极化的偶极子偏振的“抗旋转”效应：几乎没有相互作用的基础状态，这种效果与足够短波长的兴奋性相互抑制。
We study the properties of a magnetic dipolar Bose-Einstein condensate (BEC) in an elongated (cigar shaped) confining potential in the beyond quasi-one-dimensional (quasi-1D) regime. In this system the dipole-dipole interactions (DDIs) develop a momentum-dependence related to the transverse confinement and the polarization direction of the dipoles. This leads to density fluctuations being enhanced or suppressed at a length scale related to the transverse confinement length, with local atom number measurements being a practical method to observe these effects in experiments. We use meanfield theory to describe the ground state, excitations and the local number fluctuations. Quantitative predictions are presented based on full numerical solutions and a simplified variational approach that we develop. In addition to the well-known roton excitation, occurring when the dipoles are polarized along a tightly confined direction, we find an "anti-roton" effect for the case of dipoles polarized along the long axis: a nearly non-interacting ground state that experiences strongly repulsive interactions with excitations of sufficiently short wavelength.
