Optical forces and torques on atoms

Fam Le Kien, V. I. Balykin, K. Hakuta

We study the action of the force and torque induced by a guided light field on a cesium atom outside a nanofiber. We demonstrate that the evanescent light field in a circular fundamental guided mode can force the atom to rotate around the nanofiber for a macroscopic time. We find that, due to the action of the torque, the angular momentum of the atom increases with time.

Pierre Meystre

В. В. Климов, Vladilen S Letokhov

Masato Senami, Jun Nishikawa, Takaaki Hara +1 more

In this work, the novel theoretical approach to predict the torque for spin is studied. This approach is based on the novel quantities, the spin torque and the zeta force, which are proposed by one of the authors. These quantities govern the dynamics of the spin of electrons, and hence, can clarify the essential description of the dynamics of the electron spin. This approach would be applicable to many spin phenomena. In this work, as a first step of the demonstration of this approach, we investigate the spin torque and the zeta force of the dimers of alkali atoms, lithium, sodium, potassium, and rubidium.

Atsushi Hatakeyama, Runa Yasuda, Yutaka Goto +3 more

We have developed a torsion balance to detect the rotation of a cell containing spin-polarized gaseous atoms to study angular momentum transfer from gaseous atoms to solid. A cesium vapor cell was hung from a thin wire in a vacuum chamber, and irradiated from the bottom with circularly polarized light tuned to the D2 transition to polarize cesium atoms in the cell. By varying the light helicity at the resonance frequency of the torsion balance, we induced forced rotational oscillation of the cell and detected radiation torque exerted on the cesium vapor cell through the cesium atoms inside. The torque was particularly large when both hyperfine levels of cesium atoms were optically pumped with application of a longitudinal magnetic field. Further detailed study will provide new insights into spin-transfer processes at the gas-solid interface.

David E. Pritchard, Bruce G. Oldaker