We study dynamical quantum phase transitions in dilute Bose gases, for which the nonequilibrium nature of the transition becomes physically manifest in allowing for the unprecedented possibility to study many-body correlations in real time.
We explicitly investigate two such phase transitions.
The first example is bosons in an optical lattice undergoing a very rapid increase of the lattice depth, thus bringing the system quasi-instantaneously from the delocalized phase-coherent superfluid phase to the number-squeezed and localized Mott phase. The second is a
paramagnetic-ferromagnetic transition in a spinor Bose gas, in the course of which topological defects -- so-called spin vortices -- are created by a quantum version of the Kibble-Zurek scenario of second-order phase transitions. It is shown that, generically, the variance of the defect number scales with the surface area of the volume containing them.