Spinor Bose-Einstein condensates (BECs) are quantum gases where the hyperfine spin F is a free variable. They offer a rich arena for exploration since the spins can interact with one another as well as with external magnetic fields. An interplay between internal and external interactions leads to novel quantum phases and domains of different spin orientation. The image on the left shows a spin-1 BEC that has spontaneously formed spin structures with a fluctuating local value of the spin projection M_F . The cloud of atoms was subject to time-of-flight Stern-Gerlach separation of the three spin components before imaging.
We are currently focused on studying the transition from polar to antiferromagnetic phases that occurs in such a spin-1 BEC at zero quadratic Zeeman shift q (see the graphic to the left). Exactly at the transition point is a unique state of matter where the spins pair up to form a massively entangled state. We are exploring ways to detect this entanglement through measurement of spin correlations.
Links to publications:
Quantum Phase Transition in an Antiferromagnetic Spinor Bose-Einstein Condensate
Antiferromagnetic Spatial Ordering in a Quenched One-dimensional Spinor Gas