Bose-Einstein condensate (BEC) is essentially a macroscopic quantum effect with quantum volatility, macroscopic quantum coherence and artificial controllability. Owing to its unique controllability, it becomes a new ideal platform for quantum simulations and studies of interacting quantum systems.In this paper, the generation of vortices and the formation of vortex chains, as well as characteristics of vortex chains in rotating two-dimensional BEC in a potential composed of harmonic potential and optical lattice are studied numerically. Firstly, the generation of vortices, the formation and distribution of vortex chains and the effects of different physical parameters on the vortex chains in two-dimensional BEC are investigated by using the multigrid preconditioned conjugate gradient method. Secondly, the evolution of the vortex chains with time is studied by using the time-splitting spectral method. The results show that the generation of vortices in BEC trapped in the compound potential corresponds to the minimum value of the potential. When the depth of the optical lattice increases to a certain value, vortex chains are formed in the BEC. With the further increase of the depth of the optical lattice, the vortex depth in the vortex chain in the BEC decreases continuously, and finally the vortex chain disappears completely. When the interaction strength between atoms increases, the distribution range of the condensate expands, and the number of vortices and the number of vortex chains in the condensate also increase. When the interaction strength between atoms increases to a certain value, the symmetry of the vortex chains is broken. As the rotation frequency of the condensate increases, the distribution range of the condensate expands, and the number of vortices and the number of vortex chains in the condensate also increase. When the rotation frequency is close to the external trapping potential frequency, the linear alignment of the vortex chains is disrupted. It is also found that there are three stages in the evolution of the vortex chains in the BEC: in the first stage, vortex chains rotate together with the condensate, and the original chain distribution keeps unchanged; in the second stage, the phenomenon of vortex space extrusion appears, and the vortex chain is destroyed; in the third stage, the phenomenon of vortex space expansion occurs, and finally the vortex chains disappear. The results above show that the depth of the optical lattice, the interaction strength between atoms, and the rotation frequency of the condensate have important effects on the vortices and vortex chains in the condensate. By adjusting these physical quantities, the number of vortices and the shape of vortex chains in the BEC can be effectively manipulated. This may provide some theoretical reference and guidance for future experiments and applications.
液态固体电解质材料的离子电导率低,安全性问题在一定程度上限制了其发展与应用,而固体电解质材料在室温下具有很好的稳定性和高的离子电导率值,具有较好的应用前景.本文采用机械化学球磨法制备固体电解质Rb4 Cu16 I7 Cl13粉末,探索制备工艺和球磨参数,对其晶体结构进行解析、观察粉体微观结构、通过交流阻抗谱及等效电路分析得到了离子电导率与活化能、并详细探讨其离子传导性能与晶体结构的关系以及化学成分稳定性进行研究.实验结果表明,在480 rpm转速下球磨6 h时可得到纯的固体电解质Rb4 Cu16 I7 Cl13物相.粉体晶粒尺寸分布均匀,均在20 nm-400 nm之间,室温下固体电解质Rb4 Cu16 I7Cl13离子电导率可达到0.213 S/cm且活化能为0.087(9)eV.在真空干燥条件下存放5天和12天后观察了微观形貌和化学稳定性,符合阿伦尼乌斯定律.
高载流子迁移率和可调直接带隙是低维电子器件应用的两个关键特性.但目前发现的此类二维材料稀少.鉴于此在第一性原理计算的基础上,本文系统研究了In2(PS3)3单层的稳定性、电子结构性质和机械性质.研究结果表明,In2(PS3)3单层是具有直接带隙的半导体材料(1.58 eV).在-3％到3％应变下,In2(PS3)3单层的带隙是可以调节的(1.3～1.8 eV).声子谱、分子动力学和弹性常数的计算结果表明,In2(PS3)3单层是热力学、动力学和机械稳定的.此外,In2(PS3)3单层的剥离能(0.21 J m-2)小于石墨烯的剥离能(0.36 J m-2),有望像石墨烯一样机械剥离得到.这些优异的的性能使得In2(PS3)3单层有望成为未来纳米光电子设备的候选材料之一.
利用密度泛函理论结合非平衡格林函数方法，研究了不同拓扑能带结构的石墨烯电极分子器件输运特性.结果表明器件导通电压与电极禁带宽度正相关，同时器件在输运过程中表现出负微分电阻特性，峰谷电流比可达2697.分析认为器件导通源自于偏压升高过程中两电极能带匹配.器件负微分电阻特性源自于偏压升高过程中两电极能带交错.散射态分析表明，能带匹配后散射态分布较为离域，有利于电子通过器件.能带交错后散射态局域于电极处，表明电子输运受到抑制.
纳米二氧化钛（TiO 2 ）由于具有卓越的生物相容性和优异的物理性能，因此有望在生物医学领域中发挥重要的作用，且应用前景广阔.利用第一性原理计算，深入地研究了金红石型TiO 2 纳米层（110）表面与脱氧核糖核酸（DNA）不同碱基在界面之间的吸附性能及相互作用的原子机制.通过分析结合能和功函数的计算结果发现，TiO 2 纳米层（110）表面对DNA碱基的吸附强度显著增强，比典型二维纳米材料的吸附强度大两倍以上.进而，通过研究电子能带结构和态密度计算结果，阐明了二者在界面之间的吸附机制，其起源于吸附体系显著降低的能级和C、N和/或O的2p轨道与费米能级附近Ti原子的3d轨道的强烈杂化.纳米TiO 2 为DNA传感器和测序仪的设计提供了一种极具潜力的候选材料.
