Decay of an isolated monopole into a Dirac monopole

Recently, we experimentally discovered topological point defects in the polar phase of spin-1 Bose-Einstein condensates of $^{87}$Rb atoms.\footnote{M. W. Ray, E. Ruokokoski, K. Tiurev, M. M\"ott\"onen, and D. S. Hall. Observation of isolated monopoles in a quantum field. Unpublished, 2015} We numerically study the detailed decay dynamics of these isolated monopoles in experimentally realizable conditions. We find that the monopole decays by a dynamical quantum phase transition away from the polar phase. The resulting ferromagnetic order parameter is observed to exhibit a Dirac monopole in its synthetic magnetic field.\footnote{M. W. Ray, E. Ruokokoski, S. Kandel, M. M\"ott\"onen, and D. S. Hall. Observation of Dirac monopoles in a synthetic magnetic field. Nature, 505:657-660, 2014.} We furthermore show that the spin-spin interaction, quadratic Zeeman term and the three-body recombination seem to have no effect on the qualitative decay dynamics. These studies set the stage for the dynamics of topological point defects in quantum fields. Finding ways to extend the lifetime of the defect and thereafter to study the dynamics of multiple interacting point defects remains a future challenge.