Generating A Nonequilibrium Stationary State From A Ground-State Condensate Through An Almost Adiabatic Cycle

It is shown, through a mean-field description, that the ground state of weakly interacting Bose particles in a quasi-one-dimensional box trap can be converted into an excited stationary state by an almost adiabatic cyclic operation that involves a quench: A sharp impurity potential is applied, and its strength is varied during the cycle, which induces a nonequilibrium stationary state exhibiting the inversion of population. This process is robust in the sense that the resultant stationary state is almost independent of the details of the cycle, such as the position of the impurity, as long as the cycle is far enough from critical regions. The case of the failure of the population inversion due to the strong interparticle interactions is also examined.