Importance of anisotropy in the spin-liquid candidate Me3EtSb[Pd(dmit)2]2

TL;DR

This paper demonstrates that modeling Pd(dmit)2-based salts as a fully anisotropic triangular lattice significantly alters the understanding of their spin-liquid phase, emphasizing the importance of anisotropy in theoretical descriptions.

Contribution

The study introduces a fully anisotropic triangular lattice model for Pd(dmit)2 salts, showing it provides a more accurate description than the traditional t-t' model.

Findings

FATL model lowers the critical U for spin-liquid phase

Anisotropy significantly impacts electronic phase boundaries

Ab initio calculations inform more accurate models

Abstract

Organic charge transfer salts based on the molecule Pd(dmit)2 display strong electronic correlations and geometrical frustration, leading to spin liquid, valence bond solid, and superconducting states, amongst other interesting phases. The low energy electronic degrees of freedom of these materials are often described by a single band model; a triangular lattice with a molecular orbital representing a Pd(dmit)2 dimer on each site. We use ab initio electronic structure calculations to construct and parametrize low energy effective model Hamiltonians for a class of Me(4-n) EtnX[Pd(dmit)2]2 (X=As,P,N,Sb) salts and investigate how best to model these systems by using variational Monte Carlo (VMC) simulations. Our findings suggest that the prevailing model of these systems as a t-t' triangular lattice is incomplete, and that a fully anisotropic triangular lattice (FATL) description produces importantly different results, including a significant lowering of the critical U of the spin-liquid phase.