Hybrid Soliton Vortex-Ring Structures in BECs

By bringing pairs of ultra-compressed slow light pulses to a halt inside an atomic Bose-Einstein condensate, we have generated novel brands of microscopic nonlinear excitations in such zero-viscosity superfluids. These excitations are special hybrid waves made of solitons and quantized vortex rings. The solitons take the form of shape-preserving density dips that push their way through the cold-atom cloud; quantized vortices are the quantum analog of tornadoes in Bose-Einstein condensates, as their circulation must be quantized in a superfluid. Our observations directly show how solitons and vortices collide to form complex, hybrid structures with very intriguing dynamics. The vortex rings, embedded in solitonic shells, act as phantom propellers and enable the hybrid structures in the condensate to bend, like umbrellas turning inside out. They also enable the hybrid structures to merge to form closed, low-density shells, closing off and isolating tiny island of superfluid from the rest of the world. Such excitations have never before been observed. The ability to create, observe, and describe these micron-sized structures inside a Bose-Einstein condensate demonstrates the current degree of control that may be achieved in quantum fluid dynamics.

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