Quantum spin-liquid behavior in the spin-1/2 random-bond Heisenberg   antiferromagnet on the kagome lattice
  The effect of the quenched bond-randomness on the ordering of the $S=1/2$ antiferromagnetic Heisenberg model on the kagome lattice is investigated by means of an exact-diagonalization method. When the randomness exceeds a critical value, the ground state of the model exhibits a transition within the non-magnetic state into the randomness-relevant gapless spin-liquid state. Implications to the S=1/2 kagome-lattice antiferromagnet herbertsmithite is discussed. 
Hikaru Kawamura, Ken Watanabe and Tokuro Shimokawa
cond-mat.str-el cond-mat.stat-mech