2-HOLE PROBLEM IN THE T-J-MODEL - A CANONICAL TRANSFORMATION APPROACH

The t-J model in the spinless-fermion representation is studied. An ef fective Hamiltonian for the quasiparticles is derived using a canonica l transformation approach. It is shown that the rather simple form of the transformation generator allows one to take into account the effec t of hole interactions with the short-range spin waves and to describe the single-hole ground state. Obtained results are very close to ones of the self-consistent Born approximation. Further accounting of the long-range spin-wave interaction is possible on a perturbative basis. Spin-wave exchange and an effective interaction due to minimization of the number of broken antiferromagnetic bonds are included in the effe ctive quasiparticle Hamiltonian. The two-hole bound state problem is s olved using a Bethe-Salpeter equation. The only bound state found to e xist in the region of 1 <(t/J)<5 is the d wave. Both types of the hole -hole interaction are important for its formation. A discussion of the possible relation of the obtained results to the problem of supercond uctivity in real systems is presented.