论文标题
来自基于集群的投影Hartree-fock方法的海森堡旋转簇的基态
Ground states of Heisenberg spin clusters from a cluster-based projected Hartree-Fock approach
论文作者
论文摘要
预计的Hartree-Fock理论（PHF）的最新研究将近似于海森堡旋转簇的基态扩展到基于群集的ANSATZ（CPHF）。 pHF变化优化了用于恢复自旋和点组对称性的位点旋转产物状态，而CPHF组将站点放入离散的簇中，并将群集产物状态作为断裂对称参考。因此，群集内相关已在平均场水平上包括在内，并且通过对称投影引入集群间相关性。 CPHF的变体在损坏和恢复的对称性方面有不同的基础状态和抗磁性旋转环的单线 - 三个群体间隙的各种群集尺寸的差异，尽管CPHF通常对普通PHF进行了显着改善，尽管分裂分为群体降低了环形对称性。另一方面，某些二维或三维旋转布置允许群集组与完整的空间对称性兼容。因此，我们证明CPHF的蜂窝晶状体片段和对称Polyhedra具有正确的自旋和点组量子数的近似接地态。
Recent work on approximating ground states of Heisenberg spin clusters by projected Hartree-Fock theory (PHF) is extended to a cluster-based ansatz (cPHF). Whereas PHF variationally optimizes a site-spin product state for the restoration of spin- and point-group symmetry, cPHF groups sites into discrete clusters and uses a cluster-product state as the broken-symmetry reference. Intracluster correlation is thus already included at the mean-field level and intercluster correlation is introduced through symmetry projection. Variants of cPHF differing in the broken and restored symmetries are evaluated for ground states and singlet-triplet gaps of antiferromagnetic spin rings for various cluster sizes, where cPHF in general affords a significant improvement over ordinary PHF, although the division into clusters lowers the cyclical symmetry. On the other hand, certain two- or three-dimensional spin arrangements permit cluster groupings compatible with the full spatial symmetry. We accordingly demonstrate that cPHF yields approximate ground states with correct spin and point-group quantum numbers for honeycomb lattice fragments and symmetric polyhedra.
