Creating knots in spinor Bose-Einstein condensates via a Raman process

The study on three-dimensional topological defects draws a broad interest in condensed matter physics, fluid dynamics, biology, quantum information and cold atom physics. Creating three-dimensional topological defects such as knots in ultracold atomic gases is of interest because it can allow us to study the interaction and evolution of such topological features in a superfluid. In this work, we propose an experimentally feasible protocol to imprint knotted topological excitations onto the wavefunction of a dilute pseudo-spin-1/2 Bose-Einstein condensate (BEC) via a Raman process. Our calculation shows that these topological excitations can be imprinted by engineering the spatial profiles of the Raman laser fields. Additionally, we demonstrate the capability to adjust the size and the aspect ratio of the knotted nodal line by tuning the parameters of the Raman lasers.