Geometrical frustration in the spin liquid β '-Me 3EtSb[Pd(dmit) 2] 2 and the valence-bond solid Me 3EtP[Pd(dmit) 2] 2

Abstract

We show that the electronic structures of the title compounds predicted by density functional theory are well described by tight binding models. We determine the frustration ratio, J ′/J, of the Heisenberg model on the anisotropic triangular lattice, which describes the spin degrees of freedom in the Mott insulating phase for a range of Pd(dmit) 2 salts. All of the antiferromagnetic materials studied have J ′/J 0.5 or J '/J 0.9, and all salts with 0.5 J ′/J 0.9 are known, experimentally, to be charge ordered valence-bond solids or spin liquids. © 2012 American Physical Society.