Cold Bose atoms around the crossing of quantum waveguides
Cold Bose atoms around the crossing of quantum waveguides
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量子波导交叉点周围的冷玻色原子
DOI：
10.1103/physreva.89.013622
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
N. Schopohl
中科院分区：
文献类型：
--
作者：
A. Markowsky;N. Schopohl
我们表明，穿过分支区或量子波导交叉点的大量低能粒子可能会遇到无法从势中导出的非标准捕获力。对于相互作用的冷玻色原子，我们报告了三种具有破缺平移对称性的原型波导几何形状的局域 Hartree 基态的形成：曲柄 L 形波导 L、T 形波导 T 和两个量子波导的交叉 C。该现象是动能驱动的，无法用托马斯-费米近似来描述。根据各个波导 C、L、T 的连接侧管直径的比率，当粒子数 N 接近临界值时，离域开始。对于两种不同玻色原子 A 和 B 的二元混合物的情况，我们观察到两种原子种类对于亚临界粒子数的非标准捕获。当总粒子数 N=N_{A}+N_{B} 以固定混合比 N_{A}/N_{B} 增加时，会发生突然的分层量子跃迁。根据质量比 m_{A}/m_{B}，对于各种相互作用参数，较重的原子首先会离域。数值计算基于分裂方案，该方案涉及对单个粒子的虚数时间量子传播器的短时渐近的解析近似，该传播器服从各个波导内壁处的狄利克雷边界条件。
We show that massive low energy particles traversing a branching zone or a crossing of quantum waveguides may experience a non standard trapping force that cannot be derived from a potential. For interacting cold Bose atoms we report on the formation of a localised Hartree ground state for three prototype waveguide geometries with broken translational symmetry: a cranked L-shaped waveguide L, a T-shaped waveguide T, and the crossing C of two quantum waveguides. The phenomenon is kinetic energy driven and cannot be described within the Thomas-Fermi approximation. Depending on the ratio of joining lateral tube diameters of the respective waveguides C,L,T delocalisation commences when the particle number N approaches a critical value. For the case of a binary mixture of two different Bose atom species A and B we observe non standard trapping of both atom species for subcritical particle numbers. A sudden demixing quantum transition takes place as the total particle number N=N_{A}+N_{B} is increased at fixed mixing ratio N_{A}/N_{B}. Depending on the mass ratio m_{A}/m_{B} the heavier atom species delocalises first for a wide range of interaction parameters. The numerical calculations are based on a splitting scheme involving an analytic approximation to the short time asymptotics of the imaginary time quantum propagator of a single particle obeying to Dirichlet boundary conditions at the walls inside the respective waveguides.