Manipulating vortices in F=2 Bose-Einstein condensates through magnetic field and spin-orbit coupling

We investigate the vortex structures excited by Ioffe-Pritchard magnetic field and Dresselhaus-type spin-orbit coupling in F=2 ferromagnetic Bose-Einstein condensates.In the weakly interatomic interacting regime,an external magnetic field can generate a polar-core vortex in which the canonical particle current is zero.With the combined effect of spin-orbit coupling and magnetic field,the ground state experiences a transition from polar-core vortex to Mermin-Ho vortex,in which the canonical particle current is anticlockwise.For fixed spin-orbit coupling strengths,the evolution of phase winding,magnetization,and degree of phase separation with magnetic field are studied.Additionally,with further increasing spin-orbit coupling strength,the condensate exhibits symmetrical density domains separated by radial vortex arrays.Our work paves the way to explore exotic topological excitations in high-spin systems.

Vortex chains induced by anisotropic spin-orbit coupling and magnetic field in spin-2 Bose-Einstein condensates

We investigate the anisotropic spin-orbit coupled spin-2 Bose-Einstein condensates with Ioffe-Pritchard magnetic field.With nonzero magnetic field,anisotropic spin-orbit coupling will introduce several vortices and further generate a vortex chain.Inside the vortex chain,the vortices connect to each other,forming a line along the axis.The physical nature of the vortex chain can be explained by the particle current and the momentum distribution.The vortex number inside the vortex chain can be influenced via varying the magnetic field.Through adjusting the anisotropy of the spin-orbit coupling,the direction of the vortex chain is changed,and the vortex lattice can be triggered.Moreover,accompanied by the variation of the atomic interactions,the density and the momentum distribution of the vortex chain are affected.The realization and the detection of the vortex chain are compatible with current experimental techniques.

Production of Rubidium Bose-Einstein Condensate in an Optically Plugged Magnetic Quadrupole Trap

We experimentally produce the rubidium Bose-Einstein condensate in an optically plugged magnetic quadrupole trap. A far blue-detuned focused laser beam with a wavelength of 532nm is plugged in the center of the magnetic quadrupole trap to increase the number of trapped atoms and to suppress the heating. An rf evaporative cooling in the magneto-optical hybrid trap is applied to decrease the atom temperature into degeneracy. The atom number of the condensate is 1.2（0.4）× 10^5 and the temperature is below lOOnK. We also study characteristic behaviors of the condensate, such as phase space density, condensate fraction and anisotropic expansion.

High-Performance Sodium Bose-Einstein Condensate Apparatus with a Hybrid Trap and Long-Distance Magnetic Transfer

We report on the production of large sodium Bose^Einstein condensates in a hybrid of magnetic quadrupole and optical dipole trap. With an optimized spin-flip Zeeman slower, 2 ~ 1010 sodium atoms are captured in the magneto-optical trap （MOT）. A long distance magnetic transfer setup moves the cold atom over 46cm from the MOT chamber to the UHV science chamber, which provides great optical access and long conservative trap lifetime. After evaporative cooling in the hybrid trap, we produce nearly pure condensates of 1 ~ 107 atoms with lifetime of 80 s in the optical dipole trap.

Generation and control of chaos in a Bose-Einstein condensate

For a Bose-Einstein condensate （BEC） confined in a double lattice consisting of two weak laser standing waves we find the Melnikov chaotic solution and chaotic region of parameter space by using the direct perturbation method. In the chaotic region, spatial evolutions of the chaotic solution and the corresponding distribution of particle number density are bounded but unpredictable between their superior and inferior limits. It is illustrated that when the relation k1≈ k2 between the two laser wave vectors is kept, the adjustment from k2 〈 k1 to k2 ≥ k1 can transform the chaotic region into regular one or the other way round. This suggests a feasible scheme for generating and controlling chaos, which could lead to an experimental observation in the near future.

An effective method of accelerating Bose gases using magnetic coils

Based on the experimental device which is a non-uniform magnetic field to trap an atom, we show how to obtain a certain velocity of a Bose gas by controlling the magnetic coils. By comparing the relationship of the different current supply and delay time versus the ultimate velocity of the atom, we theoretically predict the method of accelerating the gases to an expected velocity. This method is of great convenience and significance for the applications in cold atom physics and precision measurements.

Dynamic stability and manipulation of bright matter-wave solitons by optical lattices in Bose-Einstein condensates

An extended variation approach to describing the dynamic evolution of self-attractive Bose-Einstein condensates is developed. We consider bright matter-wave solitons in the presence of a parabolic magnetic potential and a timespace periodic optical lattice. The dynamics of condensates is shown to be well approximated by four coupled nonlinear differential equations. A noteworthy feature is that the extended variation approach gives a critical strength ratio to support multiple stable lattice sites for the condensate. We further examine the existence of the solitons and their stabilities at the multiple stable lattice sites. In this case, the analytical predictions of Bose-Einstein condensates variational dynamics are found to be in good agreement with numerical simulations. We then find a stable region for successful manipulating matter-wave solitons without collapse, which are dragged from an initial stationary to a prescribed position by a moving periodic optical lattice.

Effects of a finite number of particles on the thermodynamic properties of a harmonically trapped ideal charged Bose gas in a constant magnetic field

We investigate the thermodynamic properties of an ideal charged Bose gas confined in an anisotropic harmonic po- tential and a constant magnetic field. Using an accurate density of states, we calculate analytically the thermodynamic potential and consequently various intriguing thermodynamic properties, including the Bose-Einstein transition tempera- ture, the specific heat, magnetization, and the corrections to these quantities due to the finite number of particles are also given explicitly. In contrast to the infinite number of particles scenarios, we show that those thermodynamic properties, particularly the Bose-Einstein transition temperature depends upon the strength of the magnetic field due to the finiteness of the particle numbers, and the collective effects of a finite number of particles become larger when the particle number decreases. Moreover, the magnetization varies with the temperature due to the finiteness of the particle number while it keeps invariant in the thermodynamic limit N -∞.

Trapped Bose-Einstein condensates in synthetic magnetic field

The rotational properties of Bose-Einstein condensates in a synthetic magnetic field are studied by numerically solving the Gross-Pitaevskii equation and comparing the results to those of condensates confined in a rotating trap. It appears to be more difficult to add a large angular momentum to condensates spun up by the synthetic magnetic field than by the rotating trap. However, strength- ening the repulsive interaction between atoms is an effective and realizable route to overcoming this problem and can at least generate vortex-lattice-like structures. In addition, the validity of the Feynman rule for condensates in the synthetic magnetic field is verified.

Effects of periodic optical lattice potential on dark solitons in a Bose Einstein condensate

This paper investigates the dynamics of dark solitons in a Bose-Einstein condensate with a magnetic trap and an optical lattice （OL） trap, and analyses the effects of the periodic OL potential on the dynamics by applying the variational approach based on the renormalized integrals of motion. The results show that the dark soliton becomes only a standing-wave and free propagation of the dark soliton is not possible when the periodic length of the OL potential is approximately equal to the effective width of the dark soliton. When the periodic length is very small or very large, the effects of the OL potential on the dark soliton will be sharply reduced. Finally, the numerical results confirm these theoretical findings.

Influences of magnetic field on the coexistence of diquark and chiral condensates in the Nambu-Jona-Lasinio model with axial anomaly

In this paper,we study the influences of magnetic fields on the coexistence of diquark and chiral condensates in an extended Nambu-Jona-Lasinio model with QCD axial anomaly,as it relates to color-flavor-locked quark matter.Due to the coupling of rotated-charged quarks to magneticfields,diquark condensates become split,and the coexistence region is thus superseded in favor of a specific diquark Bose-Einstein condensation(BEC),denoted as the BECIphase.For strong magnetic fields,we find that the BECItransition is pushed to larger quark chemical potentials.The effect of magnetic catalysis tends to disrupt the BEC-BCS(Bardeen-Cooper-Schrieffer)crossover predicted in previous works.For intermediate fields,the effect of inverse magnetic catalysis is observed,and the axial-anomaly-induced phase structure is essentially unchanged.

Unravelling-based (auto)control of back-action in atomic Bose–Einstein condensate

We present a novel feedback control method for quantum systems.Feedback does not affect the controlled system itself.Instead,it controls the unravelling of the quantum channel of interaction between the system and its environment.This interaction can be represented as a history of events.If their informational content is changed,their back-action on the system is also modified.Feedback action is trigged by the events,thus granting the system the degree of control over its own state.The efficiency of the proposed scheme is demonstrated on the example of two-mode atomic Bose-Einstein condensate,with one of its modes subject to phase-contrast imaging in a Mach–Zehnder interferometer.The histories of photocounts in the output channels of the interferometer are used for feedback.Its capabilities of state engineering are studied for different settings of the feedback loop and different numbers of events in the recorded histories.

永磁除铁过滤装置在凝结水精处理工艺中的控制系统设计研发

介绍了一种基于PLC控制的永磁除铁过滤装置控制系统,实现了对永磁除铁装置的自动化控制和监测。实验结果表明,设计的控制系统能够有效地控制永磁除铁过滤装置的运行,提高了凝结水的处理效率和质量,具有较好的实用价值和应用前景。

用于串列加速器的微团簇离子源研究

设计、安装调试了一台微团簇离子源 ,其原理是气体放电与磁控溅射相结合产生溅射粒子 ,溅射产生的粒子经过一低真空区时 ,经历液氮冷凝和复杂的碰撞 ,形成微团簇离子 ,后经高压电场引出 ,测得离子混合束的总强度 .微团簇离子束经一分析磁场 ,得到 C+ n 和 Al+ n 的质谱 。

磁传动搅拌器气氛控制装置的冷凝回流研究

利用气氛控制装置可以很好地解决磁传动搅拌器在反应釜中频繁出现内磁氢腐蚀等问题。气氛控制装置主要由冷凝回流来实现,而冷凝回流管(简称冷凝管)是实现冷凝回流的关键部件。对气氛控制装置的冷凝回流过程进行热力学计算,给出冷凝管参数的设计过程,进一步完善了磁传动搅拌器气氛控制装置的结构设计。

新一代励磁调节器平台的研制及应用

针对当前励磁调节器在工程应用中面临的新问题和新挑战,提炼出共性需求,在低频振荡抑制、主辅环协调控制、调相机控制策略、多场景支撑等方面进行了研究。提出了适应新需求的励磁调节器平台技术方案;实现了励磁调节器同步采样、双机冗余控制、闭环控制、脉冲触发、智能诊断等核心功能模块,并针对关键环节的可靠性设计进行了详细探讨。基于该技术方案研制的新一代励磁调节器已在大型电站、磁控电抗器、大型调相机上获得了成功应用。

600MW级凝结水泵节能改造技术探讨

探讨永磁调速和高压变频这两种凝结水泵改造技术,为600 MW级凝结水泵节能改造技术的选择提供参考。对比永磁调速和高压变频技术在凝结水泵实际节能改造中的节能效果、经济性、可靠性等综合指标,并选择两个机组类型、容量、运行年限相近的电厂,对两种技术在实际使用中的优劣性、节能效果、投资收益进行比较分析。结果得出:对于600 MW级凝结水泵节能改造,在可靠性方面永磁调速技术优于高压变频技术;而在系统灵活性和节能效果方面高压变频技术比永磁调速技术好。

余能发电厂凝结水泵磁力耦合器控制的改造

采用磁力耦合器控制技术对余能发电厂1#机组凝结水系统进行改造,改进了凝结水工频泵运行靠除氧器水位调节阀节流控制水位的控制方式,从而降低了凝结水泵的电耗,且通过瞬态的凝结水节流模块投入提高负荷快速响应能力和汽机经济性。