  Superfluid properties of electron-hole pairs in a quantum Hall four-layer
system are investigated. The system is considered as a solid state realization
of a two-component superfluid Bose gas with dipole-dipole interaction. One
superfluid component is formed in the top bilayer and the other component - in
the bottom one. We obtain the dispersion equation for the collective mode
spectrum and compute the critical parameters (the critical interlayer distance
and the critical currents) versus the filling factor. We find that the critical
currents of the components depend on each other. The maximum critical current
of a given component can be reached if the current of the other component is
equal to zero. The non-dissipative drag effect between the components is
studied. It is shown that in the system considered the drag factor is very
large. Under appropriate conditions it can be about 10 per sent, that is at
least in three order larder than one predicted for two-component atomic Bose
gases.
