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Subrecoil cooling of ^(6)Li atoms by 2S→3P ultraviolet narrow transition

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 36-41页

作者： Yang Rui Liang Zhang Rui Li Pengyue Liu Xuemei Liu Chunyang Duan Shichuan Yu Yuelong Wu Haibin Wu State Key Laboratory of Precision Spectroscopy Institute of Quantum Science and Precision MeasurementEast China Normal UniversityShanghai 200062China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China Shanghai Research Center for Quantum Sciences Shanghai 201315China

Laser cooling of atoms and molecules is crucial to exhibiting excellent features in the field of low-temperature physics.Cooling ^(6)Li atoms to very low temperatures is difficult due to their partially resolved D_(2) line of excited states.Here we report an observation of cooling ^(6)Li atom samples to 16μK with an ultraviolet(UV)laser in a magneto-optical trap,which breaks the Doppler cooling limit and approaches half of the photon-recoil limit.The essential mechanism of cooling results is that the natural linewidth is comparable to the recoil frequency in such a 2S→3P ultraviolet narrow transition.Laser frequency stability is important in the cooling process,and thus,the UV laser was locked to an optical frequency comb referenced to an ultrastable optical cavity.The cooling was numerically simulated to explain the cooling forces.The results can provide an ideal platform in the field of precision measurements and ultracold Fermi gases.

关键词： cold atom narrow-line UV cooling photon-recoil limit

Itinerant ferromagnetism entrenched by the anisotropy of spin-orbit coupling in a dipolar Fermi gas

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Frontiers of physics 2023年第5期18卷 227-235页

作者： Xue-Jing Feng Jin-Xin Li Lu Qin Ying-Ying Zhang ShiQiang Xia Lu Zhou ChunJie Yang ZunLue Zhu Wu-Ming Liu Xing-Dong Zhao School of Physics Henan Normal UniversityXinxiang 453000China Department of Physics School of Physics and Electronic ScienceEast China Normal UniversityShanghai 200241China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China

We investigate the itinerant ferromagnetism in a dipolar Fermi atomic system with the anisotropic spin–orbit coupling(SOC),which is traditionally explored with isotropic contact interaction.We first study the ferromagnetism transition boundaries and the properties of the ground states through the density and spin-flip distribution in momentum space,and we find that both the anisotropy and the magnitude of the SOC play an important role in this process.We propose a helpful scheme and a quantum control method which can be applied to conquering the difficulties of previous experimental observation of itinerant ferromagnetism.Our further study reveals that exotic Fermi surfaces and an abnormal phase region can exist in this system by controlling the anisotropy of SOC,which can provide constructive suggestions for the research and the application of a dipolar Fermi gas.Furthermore,we also calculate the ferromagnetism transition temperature and novel distributions in momentum space at finite temperature beyond the ground states from the perspective of experiment.

关键词： itinerant ferromagnetism spin-orbit coupling cold atom quantum simulation dipolar Fermi gas dipole-dipole interaction

Isotope separation of Potassium with a magneto–optical combined method

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Frontiers of physics 2022年第3期17卷 133-137页

作者： Zixuan Zeng Shangjin Li Bo Yan Interdisciplinary Center of Quantum Information State Key Laboratory of Modern Optical Instrumentationand Zhejiang Province Key Laboratory of Quantum Technology and Device of Physics DepartmentZhejiang UniversityHangzhou 310027China

Due to the similar physical and chemical properties, isotopes are usually hard to separate. On the other hand, the isotope shifts are very well separated in a high-resolution spectrum, making them possible to be addressed individually by lasers, thus separated. Here we report such an isotope separation experiment with Potassium atoms. The isotopes are independently optical pumped to the desired spin states, and then separated with a Stern–Gerlach scheme. A micro-capillary oven is used to collimate the atomic beam, and a Halbach-type magnet array is used to deflect the desired atoms. Finally, the 40K is enriched by two orders of magnitude. This magneto–optical combined method provides an effective way to separate isotopes and can be extended to other elements if the relevant optical pumping scheme is feasible.

关键词： cold atom isotope separation optical pumping

Precision measurement with atom interferometry

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Chinese Physics B 2015年第5期24卷 93-102页

作者：王谨 State Key Laboratory of Magnetic Resonance and atomic and Molecular Physics Wuhan Institute of Physics and MathematicsChinese Academy of Sciences Center for cold atom Physics Chinese Academy of Sciences

Development of atom interferometry and its application in precision measurement are reviewed in this paper. The principle, features and the implementation of atom interferometers are introduced, the recent progress of precision measurement with atom interferometry, including determination of gravitational constant and fine structure constant, measurement of gravity, gravity gradient and rotation, test of weak equivalence principle, proposal of gravitational wave detection, and measurement of quadratic Zeeman shift are reviewed in detail. Determination of gravitational redshift, new definition of kilogram, and measurement of weak force with atom interferometry are also briefly introduced.

关键词： cold atom atom interferometry precision measurement

Investigation of ultracold atoms and molecules in a dark magneto-optical trap

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Chinese Physics B 2012年第11期21卷 179-183页

作者：汪丽蓉姬中华元晋鹏杨艳赵延霆马杰肖连团贾锁堂 State Key Laboratory of Quantum Optics and Quantum Optics Devices Laser Spectroscopy LaboratoryShanxi University

In this paper, ultracold atoms and molecules in a dark magneto-optical trap （MOT） are studied via depumping the cesium cold atoms into the dark hyperfine ground state. The collision rate is reduced to 0.45 s-1 and the density of the atoms is increased to 5.6 × 1011 cm-3 when the fractional population of the atoms in the bright hyperfine ground state is as low as 0.15. The vibrational spectra of the ultracold cesium molecules are also studied in a standard MOT and in a dark MOT separately. The experimental results are analyzed by using the perturbative quantum approach.

关键词： cold atom dark magneto-optical trap photoassociation

Landau-like quantized levels of neutral atom induced by a dark-soliton shaped electric field

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Chinese Physics B 2020年第1期29卷 124-127页

作者：王月明靳祯 School of Physics and Electronic Engineer Shanxi UniversityTaiyuan 030006China Complex Systems Research Center Shanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

Motivated by the fascinating progresses in the cold atom experiments and theories,especially the artificial gauge field induced spin–orbit coupling of neutral atoms,we present a novel dispersion of neutral atoms carrying a non-vanishing magnetic moment in a special gauge field,an external electric field of dark-soliton shaped profile.By means of WKB approximation,we obtain discrete quantized landau-like energy levels,which is instructive for the quantum Hall effect of neutral particles.The observability of the results is also discussed.

关键词： Landau level cold atom Rashba spin–orbit coupling

Quantum reflection as the reflection of subwaves

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Chinese Physics B 2010年第9期19卷 349-353页

作者：袁文殷澄王贤平曹庄琪 Department of Physics the State Key Laboratory on Fiber Optic Local Area Communication Networks and Advanced Optical Communication SystemsShanghai Jiao Tong University Institute of Physics and Communication and Electronics Jiangxi Normal University

This paper studies quantum reflection with recent research on reflection coefficient. Based on the analytical transfer matrix method, a novel explanation for this phenomenon is proposed that quantum reflection is the reflection of subwaves, which originate inherently from the inhomogeneity of the fields and is always neglected in the semiclassical regime. Comparison with exact formula and the numerical calculations for different potentials has confirmed the reliability and the validity of the proposed theory.

关键词： quantum reflection cold atom analytical transfer matrix method

Characterizing optical dipole trap via fluorescence of trapped cesium atoms

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Science China(Physics,Mechanics & Astronomy) 2006年第3期49卷 273-280页

作者： LIU Tao, GENG Tao, YAN Shubin, LI Gang, ZHANG Jing, WANG Junmin, PENG Kunchi & ZHANG Tiancai State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-Electronics Shanxi University Taiyuan China

Optical dipole trap (ODT) is becoming an important tool of manipulating neu- tral atoms. In this paper ODT is realized with a far-off resonant laser beam strongly fo- cused in the magneto-optical trap (MOT) of cesium atoms. The light shift is measured by simply monitoring the fluorescence of the atoms in the magneto-optical trap and the opti- cal dipole trap simultaneously. The advantages of our experimental scheme are discussed, and the effect of the beam waist and power on the potential of dipole trap as well as heating rate is analyzed.

关键词： magneto-optical trap optical dipole trap cold atom light shift.

Laser cooling with adiabatic passage for type-Ⅱ transitions

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Frontiers of physics 2021年第3期16卷 193-203页

作者： Qian Liang Tao Chen Wen-Hao Bu Yu-He Zhang Bo Yan Interdisciplinary Center of Quantum Information State Key Laboratory of Modern Optical InstrumentationZhejiang Province Key Laboratory of Quantum Technology and DeviceDepartment of PhysicsZhejiang UniversityHangzhou310027China Collaborative Innovation Centre of Advanced Microstructures Nanjing UniversityNanjing210093China Key Laboratory of Quantum Optics Chinese Academy of SciencesShanghai200800China

We extend the idea of laser cooling with adiabatic passage to multi-level type-Ⅱ transitions.We find the cooling force can be significantly enhanced when a proper magnetic field is applied.That is because the magnetic field decomposes the multi-level system into several two-level sub-systems,hence the stimulated absorption and stimulated emission can occur in order,allowing for the multiple photon momentum transfer.We show that this scheme also works on the laser-coolable molecules with a better cooling effect compared to the conventional Doppler cooling.A reduced dependence on spontaneous emission based on our scheme is observed as well.Our results suggest this scheme is very feasible for laser cooling of polar molecules.

关键词： laser cooling of polar molecule adiabatic passage type-Ⅱtransition cold molecule cold atom