Instabilities dynamics in an ultra-cold Bose gas

The presence of a spin discontinuity in an ultra-cold gas has a dramatic effect on the dynamics of the system. In particular, the sudden reversal of spin across a domain wall can cause even the smallest spin perturbations to grow into macroscopic coherent oscillations. We report progress towards realizing such an instability in a magnetically trapped gas of $^{87}$Rb atoms. Using optical patterning techniques, we create a sharp spin gradient in a gas just above quantum degeneracy. We observe instability-induced rapid and sudden spin inversions and characterize their time scales.