The DSUB$m$ Approximation Scheme for the Coupled Cluster Method and Applications to Quantum Magnets

TL;DR

This paper introduces the DSUBm approximation scheme for the coupled cluster method and demonstrates its effectiveness by applying it to two quantum magnet models, showing good agreement with existing methods.

Contribution

The paper presents a novel DSUBm approximation scheme for the coupled cluster method and applies it to quantum magnet models, providing a new computational approach.

Findings

Ground-state energy results align with existing methods.

Sublattice magnetization matches known results.

Quantum critical points are accurately estimated.

Abstract

A new approximate scheme, DSUB$m$, is described for the coupled cluster method. We then apply it to two well-studied (spin-1/2 Heisenberg antiferromagnet) spin-lattice models, namely: the $XXZ$ and the $XY$ models on the square lattice in two dimensions. Results are obtained in each case for the ground-state energy, the sublattice magnetization and the quantum critical point. They are in good agreement with those from such alternative methods as spin-wave theory, series expansions, quantum Monte Carlo methods and those from the CCM using the LSUB$m$ scheme.