Studies with ultracold atoms

Lirong Wang, Jie Ma, Yanting Zhao +2 more

In the present paper, ultracold cesium atoms were obtained in magnetic optical trap using the laser cooling technology. The number of ultracold atoms is 10(7). The temperature of ultracold atoms is about 200 μK and the diameter of the ultracold atoms cloud is about 400 μm. The ultracold cesium molecules of excited states were formed using the photoassociation of ultracold atoms. The resolution of vib-rotational spectrum was studied under different scan rates of photossociation laser in the experiment. The resolution of vib-rotational spectrum becomes high when the scan rate of photossociation laser becomes slow. The cold atoms fluorescence was obtained using the high sensitive avalanche photo detector and the high resolution vib-rotational spectrum of ultracold cesium molecule in its first excited state of with dissociation limit long range state was obtained. The ultracold ground molecule was formed by controlled Raman photoassociation and the photoassociation laser must be locked to atom-molecular hyperfine transitions. The ultracold atoms photoassociation spectrum was modulated using ultra-low frequency. The first-order differential signal was optimized by changing modulation amplitude and modulation frequency. It provides a feedback signal to correct error of the laser. The laser frequency satisfies experimental requirement to form ultracold ground molecules using the controlled Raman photoassociation. This work is important for studies of ultracold atoms and molecules in confined space.

Claude N. Cohen-Tannoudji

Françoise Masnou-Seeuws, P. Pillet

Yu Wang, Qingtian Meng

Photoassociation reaction is the process in which two colliding atoms (or the colliding atom-molecule system) absorb a photon to form an excited molecule. Since the researches based on the ultracold atomic and molecular systems have attracted great attention both from theorists and experimentalists, the ultracold photoassociation reaction is becoming an ascendant research field. In this paper, we review briefly the investigation history of the photoassociation reaction for ultracold atoms, especially the basic theory of collision and the photoassociation in different light fields, and the research on the external-field manipulation of ultracold atoms collisions is also prospected.

Ren Qin, Yong Wang

We show that the magnetic field produced by a chiral ferromagnetic film can be applied to control ultracold atoms. The film will act as a magnetic mirror or a reflection grating for ultracold atoms when it is in the helical phase or the skyrmion crystal phase, respectively. By applying a bias magnetic field and a time-dependent magnetic field, one-dimensional or two-dimensional magnetic lattices including honeycomb, Kagome, and triangular types can be created to trap the ultracold atoms. We have also discussed the trapping height, the potential barrier, the trapping frequency, and the Majorana loss rate for each lattice. Our results suggest that the chiral ferromagnetic film can be a platform to develop artificial quantum systems with ultracold atoms based on modern spintronics technologies.

Yvan Castin, Jean Dalibard, Claude N. Cohen-Tannoudji