SUPERSYMMETRIC T-J MODEL - AN EXACT RESULT FOR 2 DIMENSIONS

The t-J model exhibits an additional symmetry at J = 2t. The irreducible representations of this symmetry include states with different quantities of holes and total spin. This leads to degeneracies between systems with differing number of holes and gives an upper bound on the ground-state energy for one- and two-hole systems of arbitrary dimension. Also, it leads to an exact result for the difference in the ground-state energy for momenta K = (0,0) and k = (pi,pi) between the single-hole t-J model and the Heisenberg antiferromagnet in two dimensions.