Department of Physics, Isfahan University of Technology, Isfahan, Iran.
J Phys Condens Matter. 2011 Jun 8;23(22):226006. doi: 10.1088/0953-8984/23/22/226006. Epub 2011 May 19.
We study an S = 1/2 Heisenberg model on the honeycomb lattice with first and second neighbor antiferromagnetic exchange (J(1)-J(2) model), employing exact diagonalization in both the S(z) = 0 basis and nearest neighbor singlet valence bond (NNVB) basis. We find that for 0.2 < J(2)/J(1) < 0.3, the NNVB basis gives a proper description of the ground state in comparison with the exact results. By analyzing the dimer-dimer as well as the plaquette-plaquette correlations and also defining appropriate structure factors, we investigate possible symmetry breaking states as the candidates for the ground state in the frustrated region. We provide a body of evidence in favor of plaquette valence bond ordering for 0.2 < J(2)/J(1) < 0.3. By further increasing the ratio J(2)/J(1), this state undergoes a transition to the staggered dimerized state.
我们研究了一个 S = 1/2 的海森堡模型在蜂窝晶格上，具有第一和第二近邻反铁磁交换（J(1)-J(2)模型），在 S(z) = 0 基和最近邻单重态价键（NNVB）基上都进行了精确对角化。我们发现，对于 0.2 < J(2)/J(1) < 0.3，与精确结果相比，NNVB 基给出了对基态的恰当描述。通过分析二聚体-二聚体以及 plaquette-plaquette 相关，以及定义适当的结构因子，我们研究了可能的对称破缺态作为在受挫区域的基态候选。我们提供了大量的证据，支持 plaquette 价键有序，对于 0.2 < J(2)/J(1) < 0.3。通过进一步增加 J(2)/J(1)的比值，这个态经历了从 plaquette 价键有序态到交错二聚化态的转变。
