paper

Frustrated Heisenberg antiferromagnet on the honeycomb lattice with spin quantum number

arXiv:1511.00499 · doi:10.1088/1742-6596/702/1/012001

Abstract

The ground-state (GS) phase diagram of the frustrated spin- ---- Heisenberg antiferromagnet on the honeycomb lattice is studied using the coupled cluster method, for spin quantum numbers . We study the case , in the range , which includes the point of maximum classical () frustration, viz., the classical critical point at , separating the Néel phase for and the collinear striped AFM phase for . Results are presented for the GS energy, magnetic order parameter and plaquette valence-bond crystal (PVBC) susceptibility. For all spins we find a quantum phase diagram very similar to the classical one, with a direct first-order transition between the two collinear AFM states at a value which is slightly greater than [e.g., ] and which approaches it monotonically as . By contrast, for the case the transition is split into two such that the stable GS phases are ones with Néel AFM order for and with striped AFM order for , just as in the case (for which and ). For both the and models the transition at appears to be of first-order type, while that at appears to be continuous. However, whereas in the case the intermediate phase appears to have PVBC order over the entire range , in the case PVBC ordering either exists only over a very small part of the region or, more likely, is absent everywhere.

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