QUANTUM ANTIFERROMAGNETIC SPIN 1/2 ON THE KAGOME LATTICE

A quantum antiferromagnetic system on the Kagome net with periodic boundary conditions is studied using numerical diagonalization techniques. We study clusters of sizes 9, 12, 15, 18, 21 spins (see Fig. 1), which has been used in a similar study in Ref. [1]. We found that the lowest excitations are not the usually expected spin flipping excitations. The smooth decrease of the excitation energy with the increase of system sizes indicates the existence of soft modes in the thermodynamic limit. For systems with odd number of spins, the ground states are multiply degenerate. The number of degeneracy is twice that of the classical planar model.