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Computational scheme for the spin-1/2 square lattice Heisenberg antiferromagnet based on an octapartite description of the square lattice

We introduce a novel parametrization scheme for the Hilbert space of a spin-1/2 Heisenberg antiferromagnet (AFM) based on an octapartite description of the square lattice. Our formulation provides an efficient yet systematic way to model the singlet ground-state wave function within a truncated basis. We demonstrate its effectiveness by using exact diagonalization to study systems with up to 64 spins. At significantly reduced computational cost, we obtain ground-state energies within less than 1% of the lowest values published. The non-iterative nature of this formulation and the fact that spatial symmetries remain unexploited lead to opportunities for extensions such as the incorporation into established iterative methods and the application to interacting models, for example in the study of the propagation of charged fermions in a 2D antiferromagnet.