Figure 2. Evidence of spin-liquid behaviour from Monte Carlo simulation.

(a) Classical ground-state phase diagram of (equation (1)) for J₃<0, in the plane J₄=0, showing how ordered phases with symmetry T₁, E and T₂ meet at the point J₁=J₂=0 (ref. ¹⁶). (b) Order-parameter susceptibilities and (c) heat capacity calculated in classical Monte Carlo simulation of (equation (1)), for parameters J₁=J₂=J₄=0, J₃<0. No phase transition is observed down to T=0.001 |J₃|. Instead, the order-parameter susceptibilities of neighbouring ordered phases exhibit a Curie law crossover, characteristic of a Coulombic spin-liquid⁵⁴. The symbols used for different symmetry channels are shown in the inset.