Effects of anisotropy in spin molecular-orbital coupling on effective spin models of trinuclear organometallic complexes

Abstract

We consider layered decorated honeycomb lattices at two-thirds filling, as realized in some trinuclear organometallic complexes. Localized S = 1 moments with a single-spin anisotropy emerge from the interplay of Coulomb repulsion and spin molecular-orbit coupling (SMOC). Magnetic anisotropies with bond-dependent exchange couplings occur in the honeycomb layers when the direct intracluster exchange and the spin molecular-orbital coupling are both present. We find that the effective spin exchange model within the layers is an XXZ + 120• honeycomb quantum compass model. The intrinsic nonspherical symmetry of the multinuclear complexes leads to very different transverse and longitudinal spin molecular-orbital couplings, which greatly enhances the single-spin and exchange coupling anisotropies. The interlayer coupling is described by an XXZ model with anisotropic biquadratic terms. As the correlation strength increases the system becomes increasingly one-dimensional. Thus, if the ratio of SMOC to the interlayer hopping is small this stabilizes the Haldane phase. However, as the ratio increases there is a quantum phase transition to the topologically trivial "D phase." We also predict a quantum phase transition from a Haldane phase to a magnetically ordered phase at sufficiently strong external magnetic fields.

Unconventional superconductivity near a flat band in organic and organometallic materials

“…This leads to a large density of states so one expects strong electronic correlation effects close to half filling [15]. The DHL is realized in several materials including trinuclear organometallic compounds [16][17][18][19][20], organic molecular crystals [21], iron(III) acetates [22], coordination polymers/metal-organic frameworks (MOFs) [23,24], and cold fermionic atoms in optical lattices [25]. An important open question is whether superconductivity from Coulomb interaction can arise in DHL compounds as theoretically predicted in graphene [26,27] and in the closely related lattice arising in Li-decorated graphene [28], LiC 6 .…”