Bound states in models of high-Tc superconductors

It is widely believed that the essential low-energy physics of the high-Tc CuO2 based systems is described by the t-J-like model, which contains in itself the strong interaction of local spins with mobile holes. We have studied the problem of the hole-hole interaction in an antiferromagnetic background using recently developed analytical method. Spin-wave exchange and an effective interaction due to minimization of the number of broken antiferromagnetic bonds have been taken into consideration. The bound state of the dx2-y2 symmetry has been found to be the ground state of the system in the wide region of parameters. Possible relation of the obtained results to the problem of superconductivity in real systems is discussed. (orig.)