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

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, among 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 Et n X[Pd(dmit) 2 ] 2 (X = As, P, N, Sb) salts and investigate how best to model these systems by using variational Monte Carlo 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 description produces importantly different results, including a significant lowering of the critical U of the spin-liquid phase.

Variational wave functions for theS=12Heisenberg model on the anisotropic triangular lattice: Spin liquids and spiral orders

“…In Eqs. (11)(12)(13), λ, χ, and η, as well as a 1,2,3 0 represent variational parameters to be optimized. The following Z 2 B spin liquid with a 2 × 1 unit cell (denoted by…”

Frustration, ring exchange, and the absence of long-range order inEtMe3Sb[Pd(dmit)2]2: From first principles to many-body theory

“…Previous ab initio parametrisations of a Hubbard model also fit within a quasi-1D picture, as indicated in Table II. Previous DFT studies parametrized monomer or dimer tightbinding models on the basis band structure calculations; either by fitting to models or via Wannier functions [3,4,[30][31][32]. This approach yields less anisotropy tight-binding models than our BS-DFT, as summarized in Table II, and very weak hopping between the layers [32].…”

“…Tight-binding models based on either the monomer or dimer models of EtMe 3 Sb [4,28,[30][31][32] necessarily neglect the contributions to the net exchange interactions from states outside of a small window near the Fermi energy. However, BS-DFT allows for the direct calculation of exchange interactions from the full atomistic Hamiltonian.…”

Spin-orbit coupling in Mo3S7(dmit)3

“…This approach is particularly well suited to organic and organo-metallic molecular crystals due to the separation of energy scales in this class of material [24][25][26][27]. Previous calculations on Mo 3 S 7 (dmit) 3 included only scalar relativistic effects; here we report a more intensive computation that includes a full four-component representation of the effects of relativity [28].…”