Cold matter trapping via slowly rotating helical potential

TL;DR

This paper investigates trapping cold bosonic atoms in a rotating helical optical potential created by Laguerre-Gaussian beams, analyzing superfluid dynamics and angular momentum transfer in the system.

Contribution

It introduces a novel method of trapping cold atoms using a rotating helical optical potential and analyzes the resulting superfluid behavior and angular momentum characteristics.

Findings

Angular momentum of the cloud approaches zero at zero temperature.

Toroidal traps can impart 2ℓħ angular momentum per atom.

The system's dynamics are described using superfluid hydrodynamics and Gross-Pitaevskii equation.

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.