EXACT MANY-BODY SOLUTION OF THE PERIODIC-CLUSTER T-T'-J MODEL FOR CUBIC SYSTEMS - GROUND-STATE PROPERTIES

The t-t-J model (strongly interacting limit of a particular Hubbard model) is solved exactly on small clusters of eight sites with periodic boundary conditions for the simple-, body-centered-, and face-centered-cubic lattices and for the two-dimensional square lattice. The symmetry, k vector, and spin of the ground state are studied as functions of crystalline environment, interaction strength, and electron concentration. Phase diagrams are presented for stable solutions, and regions of parameter space that exhibit ferromagnetism and heavy-fermionic behavior are identified. © 1990 The American Physical Society.