Quantum melting of the long-range antiferromagnetic order and spin-wave   condensation in t-J-V model
  We consider two-dimensional t-J-V model. The wave function of the ground state is constructed. We demonstrate that the doping by holes results in condensation of the spin-waves, destruction of the long-range antiferromagnetic order and formation of the gap in the spin-wave spectrum. 
M.Yu. Kuchiev and O. P. Sushkov