Alina Blinova (University of Massachusetts Amherst) gives a webinar on “Controlled creation and splitting of singly-quantized vortices in a polar phase BEC” at 4pm UK time.

The internal degrees of freedom of a spinor Bose-Einstein condensate (BEC) contribute to a rich phenomenology of topological excitations. Unlike their scalar counterparts, spinor BECs can support exotic vortex structures, such as singular vortices of fractionally quantized circulation and non-singular vortices of circulation that is not quantized at all. These features have been observed in the polar and ferromagnetic phases, respectively, of a spin-1 BEC. The ferromagnetic phase also hosts singly-quantized singular vortices that can undergo pair-wise annihilation even if they have the same sign of circulation. Here, we describe a set of experiments that link several aspects of these exotic vortex states. We present a method for creating a pair of singular ferromagnetic-phase vortices, each with a 2 𝜋 winding in the ferromagnetic order parameter, from a non-singular texture with a winding of 4 𝜋. In the experiment a topological interface emerges as the cores of these vortices fill with superfluid in the polar phase. This controlled creation method is also a starting point for experiments involving filled cores in different magnetic phase. For example, a swift exchange of the polar and ferromagnetic phases results in a pair of polar vortices with ferromagnetic cores. A subsequent spinor rotation, generated by an applied radio-frequency pulse, induces further evolution of the system towards two pairs of HQVs in the polar phase