Gapless spin excitations in the S=1/2 Kagome- and triangular-lattice Heisenberg antiferromagnets

The S=1/2 kagome- and triangular-lattice Heisenberg antiferromagnets are investigated using the numerical exact diagonalization and the finite-size scaling analysis. The behaviour of the field derivative at zero magnetization is examined for both systems. The present result indicates that the spin excitation is gapless for each system.