Cold matter trapping via slowly rotating helical potential

Abstract

We consider the cold bosonic ensemble trapped by a helical interference pattern in the optical \textit{loop} scheme. This rotating helical potential is produced by the two slightly detuned counter propagating Laguerre-Gaussian laser beams with counter directed orbital angular momenta $\pm \ell\hbar $. The detuning $\delta \omega$ may occur due to rotational Doppler effect. The superfluid hydrodynamics is analysed for the large number of trapped atoms in Thomas-Fermi approximation. For the highly elongated trap the Gross-Pitaevskii equation is solved in a slowly varying envelope approximation. The speed of axial translation and angular momenta of interacting atomic cloud are evaluated. In the $T \rightarrow 0$ limit the angular momentum of the helical cloud is expected to be zero while toroidal trapping geometry leads to $2\ell \hbar$ angular momentum per trapped atom.