Phase-dependent light-induced torque

Abstract

Optical torque on individual atoms in a Bose-Einstein condensate can rotate the ensemble and generate a current flow [Phys. Rev. A 82, 051402 (2010)]. We exploit the fact to suggest a new mechanism for enhanced and well-controlled rotational motions and show how atoms, interacting with Laguerre-Gaussian beams, experience a torque whose features depend on relative phase of applied fields so that zero and large positive, or even negative, values for the torque can be obtained. Such controllable torque, along with simplicity of tuning the relative phase, can simplify a possible implementation of current flows in Bose-Einstein condensates.