Mobile spin bags and their interaction in the spin-density-wave background

The motion of one doped hole in the spin-density-wave background has been studied by the variational approach. A spin-bag solution for the doped hole has been obtained that applies in the weak- and intermediate-coupling regime. The effective attraction between two spin bags with antiparallel spins has been shown to be p- and d-wave like. The low-lying spin-flip excitations are found to be important both in the spin-bag effect of the doped holes and the effective attraction between them, which, in the latter case, are combined with the exchange of the simple-amplitude fluctuations to give a dominant contribution. On the other hand, the total attractive interaction is reduced by the Coulomb repulsion, which is restored in the presence of the "bag" effect.