  Two-component systems consisting of mutually interacting particles can
demonstrate both intracomponent transport effects and intercomponent
entrainment (or drag) effects. In the presence of superfluidity, the
intracomponent transport is characterized by dissipative conductivity and
superfluid weight in the framework of two-fluid model, and intercomponent
entrainment gives rise to normal and nondissipative drag effects. We present
unified treatment of all these effects for spatially homogeneous two-component
atomic Bose-Einstein condensates based on the Bogoliubov theory, focusing
specifically on the drag effects. Calculating finite-frequency intra- and
intercomponent conductivities with taking into account quasiparticle damping,
we derive and numerically check analytical Drude-like approximations applicable
at low frequencies, and Lorentz-like approximations applicable at higher
frequencies in vicinity of the resonant energy of spin-to-density Bogoliubov
quasiparticle conversion. As possible physical realizations of two-component
atomic systems, we consider three-dimensional Bose-Bose mixtures and closely
spaced two-layered systems of magnetic dipolar atoms.
