Kravchenko L. Peculiarity of superfluidity in two-component atomic and excitonic systems.

In this thesis we study critical velocities of superfluid motion in a two-component Bose condensate, stationary waves arising at overcritical velocities of the flow and critical parameters for the superfluid state of magnetoexcitons in multilayered semiconductor systems. For two-component atomic systems the conditions on critical velocities of superfluid flow and the stability condition relative to a spatial separation of the components are obtained. We describe the stationary waves crest patterns that arise in the system under overcritical flow. Density perturbations of the components in dependence on the distance from the obstacles are obtained. A two-layer graphene system in a perpendicular to the layers magnetic field is considered. It is found that in this system a superfluid gas of electron-hole pairs is formed only in the presence of perpendicular to the layers electrical field. The dependence of the critical temperature on the interlayer distance and magnetic field is obtained. Superfluid properties of excitons in a four-layer electronic system in a perpendicular to the layers magnetic field are studied. Critical currents and critical parameters of the system are obtained. The theory of the nondissipative drag effect between superfluid excitonic components is developed.