Emergent spin-1 trimerized valence bond crystal in the spin-1/2 Heisenberg model on the star lattice


Weexplorethefrustratedspin-21 Heisenbergmodelonthestarlatticewithantiferromagnetic(AF)couplings inside each triangle and ferromagnetic (FM) intertriangle couplings (Je < 0), and calculate its magnetic and thermodynamic properties. We show that the FM couplings do not sabotage the magnetic disordering of the ground state due to the frustration from the AF interactions inside each triangle, but trigger a fully gapped inversion-symmetry-breaking trimerized valence bond crystal (TVBC) with emergent spin-1 degrees of freedom. We discover that with strengthening Je, the system exhibits a universal scaling behavior either with or without a magnetic field h: the order parameter, the five critical fields that separate the Je-h ground-state phase diagram into six phases, and the excitation gap obtained by low-temperature specific heat, all depend exponentially on Je . Our work implies that the spin-1 VBCs can be stabilized by introducing small FM couplings in the geometrically frustratedspin-21 systems.

Phys. Rev. B