Studies of one- and two-hole states in the 2D t-J model via series   expansions
  We study one and two hole properties of the t-J model at half-filling on the square lattice using series expansion methods at T=0. The dispersion curve for one hole excitations is calculated and found to be qualitatively similar to that obtained by other methods, but the bandwidth for small $t/J$ is some 20% larger than given previously. We also obtain the binding energy and dispersion relation for two hole bound states. The lowest bound state as $t/J$ increases is found to be first d-wave, and then p-wave, in accordance with predictions based upon the Kohn-Luttinger effect. We also make a similar study for the $t-J_z$ model. 
C.J. Hamer, Zheng Weihong, and J. Oitmaa (Univ. of New South Wales,   Sydney, Australia)