Geometrical frustration in the spin liquid beta'-Me3EtSb[Pd(dmit)2]2 and the valence bond solid Me3EtP[Pd(dmit)2]2

TL;DR

This paper uses DFT and tight binding models to analyze the electronic and magnetic properties of Pd(dmit)2 salts, identifying the frustration ratios that determine whether the materials are spin liquids, valence bond solids, or charge ordered.

Contribution

It provides a detailed calculation of the frustration ratio J'/J in Pd(dmit)2 salts, linking electronic structure to magnetic ground states and clarifying the conditions for different quantum phases.

Findings

Antiferromagnetic salts have J'/J < 0.5 or > 0.9.

Salts with 0.5 < J'/J < 0.9 exhibit charge order, valence bond solids, or spin liquids.

The electronic structures are well described by tight binding models.

Abstract

We show that the electronic structures of the title compounds predicted by density functional theory (DFT) 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, consistent with predictions for the Heisenberg model. All salts with 0.5 < J'/J < 0.9, where many-body theories find a number of competing ground states, are known, experimentally, to be charge ordered, valence bond solids or spin liquids.