Frustrated Heisenberg antiferromagnet on the honeycomb lattice with spin quantum number s ≥ 1

18th International Conference on Recent Progress in Many-Body Theories

Li, P.H.Y.^1 ; Bishop, R.F.^1 ; Campbell, C.E.^2

School of Physics and Astronomy, Schuster Building, University of Manchester, Manchester

M13 9PL, United Kingdom^1

School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis

MN

55455, United States^2

关键词: Coupled-cluster methods;    First order transitions;    Heisenberg antiferromagnets;    Honeycomb lattices;    Magnetic order parameter;    Quantum phase diagrams;    Spin quantum number;    Valence bond crystals;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/702/1/012001/pdf
DOI  :  10.1088/1742-6596/702/1/012001

来源: IOP

【 摘 要 】

The ground-state (GS) phase diagram of the frustrated spin-s J1-J2-J3Heisenberg antiferromagnet on the honeycomb lattice is studied using the coupled cluster method implemented to high orders of approximation, for spin quantum numbers s = 1, 3/2, 2 , 5/2. The model has antiferromagnetic (AFM) nearest-neighbour, next-nearest-neighbour and next-next-nearest-neighbour exchange couplings (with strength J1> 0, J2> 0 and J3> 0, respectively). We specifically study the case J3= J2= κJ1, in the range 0 cl= 1/2, which separates the Neel phase for κ cland the collinear striped AFM phase for κ > κcl. Results are presented for the GS energy, magnetic order parameter and plaquette valence-bond crystal (PVBC) susceptibility. For all spins s > 3/2 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 κc(s) which is slightly greater than κcl [e.g., κc(3/2) ≈ 0.53(1)] and which approaches it monotonically as s → ∞. By contrast, for the case s = 1 the transition is split into two such that the stable GS phases are one with Néel AFM order for κ c1= 0.485(5) and one with striped AFM order for κ > κc2= 0.528(5), just as in the case s = 1/2 (for which κc1≈ 0.47 and κc2≈ 0.60). For both the s = 1/2 and s = 1 models the transition at κc2appears to be of first-order type, while that at κc1appears to be continuous. However, whereas in the s = 1/2 case the intermediate phase appears to have PVBC order over the entire range κc1c2, in the s = 1 case PVBC ordering either exists only over a very small part of the region or, more likely, is absent everywhere.