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Vortices: What’s happening inside ultracold quantum storms?

Recently published computer simulation of what happens to a planar condensate of highly magnetic ultracold atoms that have been bathed in laser beams designed to enhance the interactions among the atoms.  The arrows depict the average magnetic spin orientation at that place in the condensate.  In this particular spin texture, a collection of atoms with spins pointing down (blue arrows) circulate around a sample of spin-up atoms (red arrows). Note the circulation, but in this case, the core is filled. Credit: Brandon Anderson

Vortices pop-up in the weather, sink drains, and even astrophysics; they are also a feature of quantum superfluids, such as an ultracold atomic gas. Quantum physics dictates that the circulation in these systems obeys certain quantization criteria. When a superfluid is disturbed vortices will form in order to satisfy this circulation constraint. Vortices look like mini-tornados, having an essentially empty core or “eye” with the surrounding atoms circulating.

Stirring up a superfluid is one way to induce vortices. Changing the interactions of the system can also do this—for instance introducing spin-orbit coupling.  Vortices even nucleate as a thermal gas undergoes a phase transition into a Bose-Einstein condensate. Another cool aspect: in seeking out the lowest energy configuration, the vortices will arrange into a lattice (see image below, data taken and image created by W. Ketterle group @ MIT)

Read more to learn more about coreless vortices—a quantum storm without the ‘eye.’

Recently JQI researchers used computer simulations to predict the behavior of magnetic atoms in a dipolar Bose Einstein condensate. When the atoms were subjected to additional laser beams the magnetic interactions among the atoms caused them to sort into striking spin texture patterns, including a “coreless vortex,” a condition in which one component of the atoms circulated around another component of atoms at rest in the middle (See image in above gallery).

Vortex lattice from MIT Ketterle group