Investigation of Vector Polarizability in Far-Detuned Light for Trapping Alkali Rydberg Atoms

Many experiments on ultracold atoms and molecules employ far off-resonant light, which generates an attractive trapping potential while minimizing incoherent scattering. However, for Rydberg states of alkali atoms, such light is known to be anti-trapping because of the ponderomotive force on the near-free electron. As a result, the traps are typically turned off during dipole-dipole interactions, and coherence is limited by ballistic expansion. A recent numerical calculation suggested that certain Rydberg states might possess a large vector polarizability, allowing attractive trapping with circularly polarized light. Here, we measure the vector polarizability of 54S, 54P, and 53D states of Cs atoms in optical tweezers and find values near zero, in disagreement with the numerical prediction. We show analytically that the vector polarizability vanishes in the large-n limit, where the relevant transition frequencies are small compared with the laser frequency.