An attractive BEC with a vortex in isotropic or oblate traps is found to split into two pieces via the quadrupole instability, which arises at a weaker strength of interaction than the monopole and the dipole instabilities. The split pieces rotate around the center of the trap, and subsequently unite to recover the original vortex.
Split-merge process (WMV, 254KB) (AVI, 497KB) (GIF, 904KB)
When the strength of interaction is larger, the dipole instability arises in addition to the quadrupole one. The dipole instability plays the role of transferring atoms from one to the other of the two clusters, thereby inducing the collapse.
Collapse after split-merge process (WMV, 325KB) (AVI, 841KB) (GIF, 1.39MB)
When the strength of interaction is much larger, both clusters collapse immediately after the vortex split.
Collapse after vortex split (WMV, 107KB) (AVI, 237KB) (GIF, 378KB)
